Method for performing multi-link communication in wireless communication system

ABSTRACT

According to various embodiments, a multi-link device (MLD) operating in a plurality of links including a first link can transmit a request frame to a first AP of an AP MLD through a first STA (station), wherein the request frame includes an information field for requesting every element included in an element set designated for a second link. The MLD can, on the basis of the request frame, receive every element included in the element set designated for the second link.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

The present specification relates to a method for performing multi-linkcommunication in a wireless local area network (WLAN) system and, mostparticularly, to a method for transmitting information on a link in amulti-link communication and a device for supporting the same.

Related Art

Wireless network technologies may include various types of wirelesslocal area networks (WLANs). The WLAN employs widely used networkingprotocols and can be used to interconnect nearby devices together. Thevarious technical features described herein may be applied to anycommunication standard, such as WiFi or, more generally, any one of theIEEE 802.11 family of wireless protocols. A wireless local area network(WLAN) has been enhanced in various ways. For example, the IEEE 802.11axstandard has proposed an enhanced communication environment by usingorthogonal frequency division multiple access (OFDMA) and downlinkmulti-user multiple input multiple output (DL MU MIMO) schemes.

The present specification proposes a technical feature that can beutilized in a new communication standard. For example, the newcommunication standard may be an extreme high throughput (EHT) standardwhich is currently being discussed. The EHT standard may use anincreased bandwidth, an enhanced PHY layer protocol data unit (PPDU)structure, an enhanced sequence, a hybrid automatic repeat request(HARQ) scheme, or the like, which is newly proposed. The EHT standardmay be called the IEEE 802.11be standard.

SUMMARY OF THE DISCLOSURE

Technical Objects

In the EHT specification, in order to support high throughput and highdata rate, a wide bandwidth (e.g., 160/320 MHz), 16 streams, and/or amulti-link (or multi-band) operation, and so on, may be used.

In the EHT specification, a device supporting multi-link (i.e., amulti-link device) may operate on a plurality of links. In order toswitch a connected link, a multi-link device may need to receiveinformation on another link that is not a link included in the pluralityof links. Therefore, a technical characteristic enabling a multi-linkdevice to receive information on another link that is not connected tothe multi-link device may be required in the multi-link device.

Additionally, while performing communication through a first link, themulti-link device needs to receive information on at least one linkamong the plurality of links. Therefore, the multi-link device mayrequire a technical characteristic enabling the multi-link device toreceive information on another link.

Technical Solutions

According to various embodiments, a multi-link device (MLD) connected toa plurality of links including a first link may perform the steps oftransmitting a request frame including an information field forrequesting complete elements included in an element set designated for asecond link to a first access point (AP) of an AP multi-link device,through a first station (STA) included in the multi-link device, whereinthe first STA operates on the first link, and receiving a response framefrom the first AP through the first STA, based on the request frame,wherein the response frame includes complete elements included in theelement set designated for the second link.

Effects of the Disclosure

An STA included in a multi-link device may deliver information relatedto other STAs within the multi-link device together through one link.Therefore, overhead of frame exchange may be reduced. Additionally, linkusage efficiency of the STA may be increased, and power consumption maybe reduced.

Additionally, a first STA included in the multi-link device may requestall information per link. For example, the first STA of the multi-linkdevice may request all information related to a second link and mayrequest only partial information related to a third link. Therefore,since the first STA may request all information per link, an APmulti-link device may transmit all information related to an indicatedlink.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a transmitting apparatus and/or receivingapparatus of the present specification.

FIG. 2 is a conceptual view illustrating the structure of a wirelesslocal area network (WLAN).

FIG. 3 illustrates a general link setup process.

FIG. 4 illustrates an example of a PPDU used in an IEEE standard.

FIG. 5 illustrates a layout of resource units (RUs) used in a band of 20MHz.

FIG. 6 illustrates a layout of RUs used in a band of 40 MHz.

FIG. 7 illustrates a layout of RUs used in a band of 80 MHz.

FIG. 8 illustrates a structure of an HE-SIG-B field.

FIG. 9 illustrates an example in which a plurality of user STAs areallocated to the same RU through a MU-MIMO scheme.

FIG. 10 illustrates an operation based on UL-MU.

FIG. 11 illustrates an example of a trigger frame.

FIG. 12 illustrates an example of a common information field of atrigger frame.

FIG. 13 illustrates an example of a subfield included in a per userinformation field.

FIG. 14 describes a technical feature of the UORA scheme.

FIG. 15 illustrates an example of a channel used/supported/definedwithin a 2.4 GHz band.

FIG. 16 illustrates an example of a channel used/supported/definedwithin a 5 GHz band.

FIG. 17 illustrates an example of a channel used/supported/definedwithin a 6 GHz band.

FIG. 18 illustrates an example of a PPDU used in the presentspecification.

FIG. 19 illustrates an example of a modified transmission device and/orreceiving device of the present specification.

FIG. 20 shows an example of a HE-PPDU.

FIG. 21 shows an example of channel bonding.

FIG. 22 shows an exemplary structure of a non-AP MLD.

FIG. 23 shows an exemplary connection between an AP MLD and a non-AP MLDthrough a Link setup process.

FIG. 24 shows an example of a link being switched or reconnected.

FIG. 25 shows a detailed example of a link being switched orreconnected.

FIG. 26 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

FIG. 27 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

FIG. 28 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

FIG. 29 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

FIG. 30 shows an operation on a non-AP MLD for requesting information onother AP(s).

FIG. 31 shows a detailed example of an STA ratio per Link

FIG. 32 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

FIG. 33 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

FIG. 34 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

FIG. 35 shows an example of an MLD structure supporting anchoredlink(s).

FIG. 36 shows an example of a situation where anchored link switching orreconnection is needed.

FIG. 37 shows operations of an AP MLD and a non-AP MLD for anchored linkswitching or reconnection.

FIG. 38 and FIG. 39 respectively show detailed examples of elements foranchored link reconnection.

FIG. 40 shows a detailed example of a Request element format.

FIG. 41 shows a detailed example of an Extended Request element format.

FIG. 42 shows a detailed example of a PV1 Probe Response Option elementformat.

FIG. 43 is a flowchart describing operations of a multi-link device.

FIG. 44 is a flowchart describing operations of an AP multi-link device.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the present specification, “A or B” may mean “only A”, “only B” or“both A and B”. In other words, in the present specification, “A or B”may be interpreted as “A and/or B”. For example, in the presentspecification, “A, B, or C” may mean “only A”, “only B”, “only C”, or“any combination of A, B, C”.

A slash (/) or comma used in the present specification may mean“and/or”. For example, “A/B” may mean “A and/or B”. Accordingly, “A/B”may mean “only A”, “only B”, or “both A and B”. For example, “A, B, C”may mean “A, B, or C”.

In the present specification, “at least one of A and B” may mean “onlyA”, “only B”, or “both A and B”. In addition, in the presentspecification, the expression “at least one of A or B” or “at least oneof A and/or B” may be interpreted as “at least one of A and B”.

In addition, in the present specification, “at least one of A, B, and C”may mean “only A”, “only B”, “only C”, or “any combination of A, B, andC”. In addition, “at least one of A, B, or C” or “at least one of A, B,and/or C” may mean “at least one of A, B, and C”.

In addition, a parenthesis used in the present specification may mean“for example”. Specifically, when indicated as “control information(EHT-signal)”, it may denote that “EHT-signal” is proposed as an exampleof the “control information”. In other words, the “control information”of the present specification is not limited to “EHT-signal”, and“EHT-signal” may be proposed as an example of the “control information”.In addition, when indicated as “control information (i.e., EHT-signal)”,it may also mean that “EHT-signal” is proposed as an example of the“control information”.

Technical features described individually in one figure in the presentspecification may be individually implemented, or may be simultaneouslyimplemented.

The following example of the present specification may be applied tovarious wireless communication systems. For example, the followingexample of the present specification may be applied to a wireless localarea network (WLAN) system. For example, the present specification maybe applied to the IEEE 802.11a/g/n/ac standard or the IEEE 802.11axstandard. In addition, the present specification may also be applied tothe newly proposed EHT standard or IEEE 802.11be standard. In addition,the example of the present specification may also be applied to a newWLAN standard enhanced from the EHT standard or the IEEE 802.11bestandard. In addition, the example of the present specification may beapplied to a mobile communication system. For example, it may be appliedto a mobile communication system based on long term evolution (LTE)depending on a 3^(rd) generation partnership project (3GPP) standard andbased on evolution of the LTE. In addition, the example of the presentspecification may be applied to a communication system of a 5G NRstandard based on the 3GPP standard.

Hereinafter, in order to describe a technical feature of the presentspecification, a technical feature applicable to the presentspecification will be described.

FIG. 1 shows an example of a transmitting apparatus and/or receivingapparatus of the present specification.

In the example of FIG. 1 , various technical features described belowmay be performed. FIG. 1 relates to at least one station (STA). Forexample, STAs 110 and 120 of the present specification may also becalled in various terms such as a mobile terminal, a wireless device, awireless transmit/receive unit (WTRU), a user equipment (UE), a mobilestation (MS), a mobile subscriber unit, or simply a user. The STAs 110and 120 of the present specification may also be called in various termssuch as a network, a base station, a node-B, an access point (AP), arepeater, a router, a relay, or the like. The STAs 110 and 120 of thepresent specification may also be referred to as various names such as areceiving apparatus, a transmitting apparatus, a receiving STA, atransmitting STA, a receiving device, a transmitting device, or thelike.

For example, the STAs 110 and 120 may serve as an AP or a non-AP. Thatis, the STAs 110 and 120 of the present specification may serve as theAP and/or the non-AP.

The STAs 110 and 120 of the present specification may support variouscommunication standards together in addition to the IEEE 802.11standard. For example, a communication standard (e.g., LTE, LTE-A, 5G NRstandard) or the like based on the 3GPP standard may be supported. Inaddition, the STA of the present specification may be implemented asvarious devices such as a mobile phone, a vehicle, a personal computer,or the like. In addition, the STA of the present specification maysupport communication for various communication services such as voicecalls, video calls, data communication, and self-driving(autonomous-driving), or the like.

The STAs 110 and 120 of the present specification may include a mediumaccess control (MAC) conforming to the IEEE 802.11 standard and aphysical layer interface for a radio medium.

The STAs 110 and 120 will be described below with reference to asub-figure (a) of FIG. 1 .

The first STA 110 may include a processor 111, a memory 112, and atransceiver 113. The illustrated process, memory, and transceiver may beimplemented individually as separate chips, or at least twoblocks/functions may be implemented through a single chip.

The transceiver 113 of the first STA performs a signaltransmission/reception operation. Specifically, an IEEE 802.11 packet(e.g., IEEE 802.11a/b/g/n/ac/ax/be, etc.) may be transmitted/received.

For example, the first STA 110 may perform an operation intended by anAP. For example, the processor 111 of the AP may receive a signalthrough the transceiver 113, process a reception (RX) signal, generate atransmission (TX) signal, and provide control for signal transmission.The memory 112 of the AP may store a signal (e.g., RX signal) receivedthrough the transceiver 113, and may store a signal (e.g., TX signal) tobe transmitted through the transceiver.

For example, the second STA 120 may perform an operation intended by anon-AP STA. For example, a transceiver 123 of a non-AP performs a signaltransmission/reception operation. Specifically, an IEEE 802.11 packet(e.g., IEEE 802.11a/b/g/n/ac/ax/be packet, etc.) may betransmitted/received.

For example, a processor 121 of the non-AP STA may receive a signalthrough the transceiver 123, process an RX signal, generate a TX signal,and provide control for signal transmission. A memory 122 of the non-APSTA may store a signal (e.g., RX signal) received through thetransceiver 123, and may store a signal (e.g., TX signal) to betransmitted through the transceiver.

For example, an operation of a device indicated as an AP in thespecification described below may be performed in the first STA 110 orthe second STA 120. For example, if the first STA 110 is the AP, theoperation of the device indicated as the AP may be controlled by theprocessor 111 of the first STA 110, and a related signal may betransmitted or received through the transceiver 113 controlled by theprocessor 111 of the first STA 110. In addition, control informationrelated to the operation of the AP or a TX/RX signal of the AP may bestored in the memory 112 of the first STA 110. In addition, if thesecond STA 120 is the AP, the operation of the device indicated as theAP may be controlled by the processor 121 of the second STA 120, and arelated signal may be transmitted or received through the transceiver123 controlled by the processor 121 of the second STA 120. In addition,control information related to the operation of the AP or a TX/RX signalof the AP may be stored in the memory 122 of the second STA 120.

For example, in the specification described below, an operation of adevice indicated as a non-AP (or user-STA) may be performed in the firstSTA 110 or the second STA 120. For example, if the second STA 120 is thenon-AP, the operation of the device indicated as the non-AP may becontrolled by the processor 121 of the second STA 120, and a relatedsignal may be transmitted or received through the transceiver 123controlled by the processor 121 of the second STA 120. In addition,control information related to the operation of the non-AP or a TX/RXsignal of the non-AP may be stored in the memory 122 of the second STA120. For example, if the first STA 110 is the non-AP, the operation ofthe device indicated as the non-AP may be controlled by the processor111 of the first STA 110, and a related signal may be transmitted orreceived through the transceiver 113 controlled by the processor 111 ofthe first STA 110. In addition, control information related to theoperation of the non-AP or a TX/RX signal of the non-AP may be stored inthe memory 112 of the first STA 110.

In the specification described below, a device called a(transmitting/receiving) STA, a first STA, a second STA, a STA1, a STA2,an AP, a first AP, a second AP, an AP1, an AP2, a(transmitting/receiving) terminal, a (transmitting/receiving) device, a(transmitting/receiving) apparatus, a network, or the like may imply theSTAs 110 and 120 of FIG. 1 . For example, a device indicated as, withouta specific reference numeral, the (transmitting/receiving) STA, thefirst STA, the second STA, the STA1, the STA2, the AP, the first AP, thesecond AP, the AP1, the AP2, the (transmitting/receiving) terminal, the(transmitting/receiving) device, the (transmitting/receiving) apparatus,the network, or the like may imply the STAs 110 and 120 of FIG. 1 . Forexample, in the following example, an operation in which various STAstransmit/receive a signal (e.g., a PPDU) may be performed in thetransceivers 113 and 123 of FIG. 1 . In addition, in the followingexample, an operation in which various STAs generate a TX/RX signal orperform data processing and computation in advance for the TX/RX signalmay be performed in the processors 111 and 121 of FIG. 1 . For example,an example of an operation for generating the TX/RX signal or performingthe data processing and computation in advance may include: 1) anoperation ofdetermining/obtaining/configuring/computing/decoding/encoding bitinformation of a sub-field (SIG, STF, LTF, Data) included in a PPDU; 2)an operation of determining/configuring/obtaining a time resource orfrequency resource (e.g., a subcarrier resource) or the like used forthe sub-field (SIG, STF, LTF, Data) included the PPDU; 3) an operationof determining/configuring/obtaining a specific sequence (e.g., a pilotsequence, an STF/LTF sequence, an extra sequence applied to SIG) or thelike used for the sub-field (SIG, STF, LTF, Data) field included in thePPDU; 4) a power control operation and/or power saving operation appliedfor the STA; and 5) an operation related todetermining/obtaining/configuring/decoding/encoding or the like of anACK signal. In addition, in the following example, a variety ofinformation used by various STAs fordetermining/obtaining/configuring/computing/decoding/decoding a TX/RXsignal (e.g., information related to a field/subfield/controlfield/parameter/power or the like) may be stored in the memories 112 and122 of FIG. 1 .

The aforementioned device/STA of the sub-figure (a) of FIG. 1 may bemodified as shown in the sub-figure (b) of FIG. 1 . Hereinafter, theSTAs 110 and 120 of the present specification will be described based onthe sub-figure (b) of FIG. 1 .

For example, the transceivers 113 and 123 illustrated in the sub-figure(b) of FIG. 1 may perform the same function as the aforementionedtransceiver illustrated in the sub-figure (a) of FIG. 1 . For example,processing chips 114 and 124 illustrated in the sub-figure (b) of FIG. 1may include the processors 111 and 121 and the memories 112 and 122. Theprocessors 111 and 121 and memories 112 and 122 illustrated in thesub-figure (b) of FIG. 1 may perform the same function as theaforementioned processors 111 and 121 and memories 112 and 122illustrated in the sub-figure (a) of FIG. 1 .

A mobile terminal, a wireless device, a wireless transmit/receive unit(WTRU), a user equipment (UE), a mobile station (MS), a mobilesubscriber unit, a user, a user STA, a network, a base station, aNode-B, an access point (AP), a repeater, a router, a relay, a receivingunit, a transmitting unit, a receiving STA, a transmitting STA, areceiving device, a transmitting device, a receiving apparatus, and/or atransmitting apparatus, which are described below, may imply the STAs110 and 120 illustrated in the sub-figure (a)/(b) of FIG. 1 , or mayimply the processing chips 114 and 124 illustrated in the sub-figure (b)of FIG. 1 . That is, a technical feature of the present specificationmay be performed in the STAs 110 and 120 illustrated in the sub-figure(a)/(b) of FIG. 1 , or may be performed only in the processing chips 114and 124 illustrated in the sub-figure (b) of FIG. 1 . For example, atechnical feature in which the transmitting STA transmits a controlsignal may be understood as a technical feature in which a controlsignal generated in the processors 111 and 121 illustrated in thesub-figure (a)/(b) of FIG. 1 is transmitted through the transceivers 113and 123 illustrated in the sub-figure (a)/(b) of FIG. 1 . Alternatively,the technical feature in which the transmitting STA transmits thecontrol signal may be understood as a technical feature in which thecontrol signal to be transferred to the transceivers 113 and 123 isgenerated in the processing chips 114 and 124 illustrated in thesub-figure (b) of FIG. 1 .

For example, a technical feature in which the receiving STA receives thecontrol signal may be understood as a technical feature in which thecontrol signal is received by means of the transceivers 113 and 123illustrated in the sub-figure (a) of FIG. 1 . Alternatively, thetechnical feature in which the receiving STA receives the control signalmay be understood as the technical feature in which the control signalreceived in the transceivers 113 and 123 illustrated in the sub-figure(a) of FIG. 1 is obtained by the processors 111 and 121 illustrated inthe sub-figure (a) of FIG. 1 . Alternatively, the technical feature inwhich the receiving STA receives the control signal may be understood asthe technical feature in which the control signal received in thetransceivers 113 and 123 illustrated in the sub-figure (b) of FIG. 1 isobtained by the processing chips 114 and 124 illustrated in thesub-figure (b) of FIG. 1 .

Referring to the sub-figure (b) of FIG. 1 , software codes 115 and 125may be included in the memories 112 and 122. The software codes 115 and126 may include instructions for controlling an operation of theprocessors 111 and 121. The software codes 115 and 125 may be includedas various programming languages.

The processors 111 and 121 or processing chips 114 and 124 of FIG. 1 mayinclude an application-specific integrated circuit (ASIC), otherchipsets, a logic circuit and/or a data processing device. The processormay be an application processor (AP). For example, the processors 111and 121 or processing chips 114 and 124 of FIG. 1 may include at leastone of a digital signal processor (DSP), a central processing unit(CPU), a graphics processing unit (GPU), and a modulator and demodulator(modem). For example, the processors 111 and 121 or processing chips 114and 124 of FIG. 1 may be SNAPDRAGON™ series of processors made byQualcomm®, EXYNOS™ series of processors made by Samsung®, A series ofprocessors made by Apple®, HELIO™ series of processors made byMediaTek®, ATOM™ series of processors made by Intel® or processorsenhanced from these processors.

In the present specification, an uplink may imply a link forcommunication from a non-AP STA to an SP STA, and an uplinkPPDU/packet/signal or the like may be transmitted through the uplink. Inaddition, in the present specification, a downlink may imply a link forcommunication from the AP STA to the non-AP STA, and a downlinkPPDU/packet/signal or the like may be transmitted through the downlink.

FIG. 2 is a conceptual view illustrating the structure of a wirelesslocal area network (WLAN).

An upper part of FIG. 2 illustrates the structure of an infrastructurebasic service set (BSS) of institute of electrical and electronicengineers (IEEE) 802.11.

Referring the upper part of FIG. 2 , the wireless LAN system may includeone or more infrastructure BSSs 200 and 205 (hereinafter, referred to asBSS). The BSSs 200 and 205 as a set of an AP and a STA such as an accesspoint (AP) 225 and a station (STA1) 200-1 which are successfullysynchronized to communicate with each other are not concepts indicatinga specific region. The BSS 205 may include one or more STAs 205-1 and205-2 which may be joined to one AP 230.

The BSS may include at least one STA, APs providing a distributionservice, and a distribution system (DS) 210 connecting multiple APs.

The distribution system 210 may implement an extended service set (ESS)240 extended by connecting the multiple BSSs 200 and 205. The ESS 240may be used as a term indicating one network configured by connectingone or more APs 225 or 230 through the distribution system 210. The APincluded in one ESS 240 may have the same service set identification(SSID).

A portal 220 may serve as a bridge which connects the wireless LANnetwork (IEEE 802.11) and another network (e.g., 802.X).

In the BSS illustrated in the upper part of FIG. 2 , a network betweenthe APs 225 and 230 and a network between the APs 225 and 230 and theSTAs 200-1, 205-1, and 205-2 may be implemented. However, the network isconfigured even between the STAs without the APs 225 and 230 to performcommunication. A network in which the communication is performed byconfiguring the network even between the STAs without the APs 225 and230 is defined as an Ad-Hoc network or an independent basic service set(IBSS).

A lower part of FIG. 2 illustrates a conceptual view illustrating theIBSS.

Referring to the lower part of FIG. 2 , the IBSS is a BSS that operatesin an Ad-Hoc mode. Since the IBSS does not include the access point(AP), a centralized management entity that performs a managementfunction at the center does not exist. That is, in the IBSS, STAs 250-1,250-2, 250-3, 255-4, and 255-5 are managed by a distributed manner. Inthe IBSS, all STAs 250-1, 250-2, 250-3, 255-4, and 255-5 may beconstituted by movable STAs and are not permitted to access the DS toconstitute a self-contained network.

FIG. 3 illustrates a general link setup process.

In S310, a STA may perform a network discovery operation. The networkdiscovery operation may include a scanning operation of the STA. Thatis, to access a network, the STA needs to discover a participatingnetwork. The STA needs to identify a compatible network beforeparticipating in a wireless network, and a process of identifying anetwork present in a particular area is referred to as scanning.Scanning methods include active scanning and passive scanning.

FIG. 3 illustrates a network discovery operation including an activescanning process. In active scanning, a STA performing scanningtransmits a probe request frame and waits for a response to the proberequest frame in order to identify which AP is present around whilemoving to channels. A responder transmits a probe response frame as aresponse to the probe request frame to the STA having transmitted theprobe request frame. Here, the responder may be a STA that transmits thelast beacon frame in a BSS of a channel being scanned. In the BSS, sincean AP transmits a beacon frame, the AP is the responder. In an IBSS,since STAs in the IBSS transmit a beacon frame in turns, the responderis not fixed. For example, when the STA transmits a probe request framevia channel 1 and receives a probe response frame via channel 1, the STAmay store BSS-related information included in the received proberesponse frame, may move to the next channel (e.g., channel 2), and mayperform scanning (e.g., transmits a probe request and receives a proberesponse via channel 2) by the same method.

Although not shown in FIG. 3 , scanning may be performed by a passivescanning method. In passive scanning, a STA performing scanning may waitfor a beacon frame while moving to channels. A beacon frame is one ofmanagement frames in IEEE 802.11 and is periodically transmitted toindicate the presence of a wireless network and to enable the STAperforming scanning to find the wireless network and to participate inthe wireless network. In a BSS, an AP serves to periodically transmit abeacon frame. In an IBSS, STAs in the IBSS transmit a beacon frame inturns. Upon receiving the beacon frame, the STA performing scanningstores information related to a BSS included in the beacon frame andrecords beacon frame information in each channel while moving to anotherchannel. The STA having received the beacon frame may store BSS-relatedinformation included in the received beacon frame, may move to the nextchannel, and may perform scanning in the next channel by the samemethod.

After discovering the network, the STA may perform an authenticationprocess in S320. The authentication process may be referred to as afirst authentication process to be clearly distinguished from thefollowing security setup operation in S340. The authentication processin S320 may include a process in which the STA transmits anauthentication request frame to the AP and the AP transmits anauthentication response frame to the STA in response. The authenticationframes used for an authentication request/response are managementframes.

The authentication frames may include information related to anauthentication algorithm number, an authentication transaction sequencenumber, a status code, a challenge text, a robust security network(RSN), and a finite cyclic group.

The STA may transmit the authentication request frame to the AP. The APmay determine whether to allow the authentication of the STA based onthe information included in the received authentication request frame.The AP may provide the authentication processing result to the STA viathe authentication response frame.

When the STA is successfully authenticated, the STA may perform anassociation process in S330. The association process includes a processin which the STA transmits an association request frame to the AP andthe AP transmits an association response frame to the STA in response.The association request frame may include, for example, informationrelated to various capabilities, a beacon listen interval, a service setidentifier (SSID), a supported rate, a supported channel, RSN, amobility domain, a supported operating class, a traffic indication map(TIM) broadcast request, and an interworking service capability. Theassociation response frame may include, for example, information relatedto various capabilities, a status code, an association ID (AID), asupported rate, an enhanced distributed channel access (EDCA) parameterset, a received channel power indicator (RCPI), a receivedsignal-to-noise indicator (RSNI), a mobility domain, a timeout interval(association comeback time), an overlapping BSS scanning parameter, aTIM broadcast response, and a QoS map.

In S340, the STA may perform a security setup process. The securitysetup process in S340 may include a process of setting up a private keythrough four-way handshaking, for example, through an extensibleauthentication protocol over LAN (EAPOL) frame.

FIG. 4 illustrates an example of a PPDU used in an IEEE standard.

As illustrated, various types of PHY protocol data units (PPDUs) areused in IEEE a/g/n/ac standards. Specifically, an LTF and a STF includea training signal, a SIG-A and a SIG-B include control information for areceiving STA, and a data field includes user data corresponding to aPSDU (MAC PDU/aggregated MAC PDU).

FIG. 4 also includes an example of an HE PPDU according to IEEE802.11ax. The HE PPDU according to FIG. 4 is an illustrative PPDU formultiple users. An HE-SIG-B may be included only in a PPDU for multipleusers, and an HE-SIG-B may be omitted in a PPDU for a single user.

As illustrated in FIG. 4 , the HE-PPDU for multiple users (MUs) mayinclude a legacy-short training field (L-STF), a legacy-long trainingfield (L-LTF), a legacy-signal (L-SIG), a high efficiency-signal A(HE-SIG A), a high efficiency-signal-B (HE-SIG B), a highefficiency-short training field (HE-STF), a high efficiency-longtraining field (HE-LTF), a data field (alternatively, an MAC payload),and a packet extension (PE) field. The respective fields may betransmitted for illustrated time periods (i.e., 4 or 8 μs).

Hereinafter, a resource unit (RU) used for a PPDU is described. An RUmay include a plurality of subcarriers (or tones). An RU may be used totransmit a signal to a plurality of STAs according to OFDMA. Further, anRU may also be defined to transmit a signal to one STA. An RU may beused for an STF, an LTF, a data field, or the like.

FIG. 5 illustrates a layout of resource units (RUs) used in a band of 20MHz.

As illustrated in FIG. 5 , resource units (RUs) corresponding todifferent numbers of tones (i.e., subcarriers) may be used to form somefields of an HE-PPDU. For example, resources may be allocated inillustrated RUs for an HE-STF, an HE-LTF, and a data field.

As illustrated in the uppermost part of FIG. 5 , a 26-unit (i.e., a unitcorresponding to 26 tones) may be disposed. Six tones may be used for aguard band in the leftmost band of the 20 MHz band, and five tones maybe used for a guard band in the rightmost band of the 20 MHz band.Further, seven DC tones may be inserted in a center band, that is, a DCband, and a 26-unit corresponding to 13 tones on each of the left andright sides of the DC band may be disposed. A 26-unit, a 52-unit, and a106-unit may be allocated to other bands. Each unit may be allocated fora receiving STA, that is, a user.

The layout of the RUs in FIG. 5 may be used not only for a multipleusers (MUs) but also for a single user (SU), in which case one 242-unitmay be used and three DC tones may be inserted as illustrated in thelowermost part of FIG. 5 .

Although FIG. 5 proposes RUs having various sizes, that is, a 26-RU, a52-RU, a 106-RU, and a 242-RU, specific sizes of RUs may be extended orincreased. Therefore, the present embodiment is not limited to thespecific size of each RU (i.e., the number of corresponding tones).

FIG. 6 illustrates a layout of RUs used in a band of 40 MHz.

Similarly to FIG. 5 in which RUs having various sizes are used, a 26-RU,a 52-RU, a 106-RU, a 242-RU, a 484-RU, and the like may be used in anexample of FIG. 6 . Further, five DC tones may be inserted in a centerfrequency, 12 tones may be used for a guard band in the leftmost band ofthe 40 MHz band, and 11 tones may be used for a guard band in therightmost band of the 40 MHz band.

As illustrated in FIG. 6 , when the layout of the RUs is used for asingle user, a 484-RU may be used. The specific number of RUs may bechanged similarly to FIG. 5 .

FIG. 7 illustrates a layout of RUs used in a band of 80 MHz.

Similarly to FIG. 5 and FIG. 6 in which RUs having various sizes areused, a 26-RU, a 52-RU, a 106-RU, a 242-RU, a 484-RU, a 996-RU, and thelike may be used in an example of FIG. 7 . Further, seven DC tones maybe inserted in the center frequency, 12 tones may be used for a guardband in the leftmost band of the 80 MHz band, and 11 tones may be usedfor a guard band in the rightmost band of the 80 MHz band. In addition,a 26-RU corresponding to 13 tones on each of the left and right sides ofthe DC band may be used.

As illustrated in FIG. 7 , when the layout of the RUs is used for asingle user, a 996-RU may be used, in which case five DC tones may beinserted.

The RU described in the present specification may be used in uplink (UL)communication and downlink (DL) communication. For example, when UL-MUcommunication which is solicited by a trigger frame is performed, atransmitting STA (e.g., an AP) may allocate a first RU (e.g.,26/52/106/242-RU, etc.) to a first STA through the trigger frame, andmay allocate a second RU (e.g., 26/52/106/242-RU, etc.) to a second STA.Thereafter, the first STA may transmit a first trigger-based PPDU basedon the first RU, and the second STA may transmit a second trigger-basedPPDU based on the second RU. The first/second trigger-based PPDU istransmitted to the AP at the same (or overlapped) time period.

For example, when a DL MU PPDU is configured, the transmitting STA(e.g., AP) may allocate the first RU (e.g., 26/52/106/242-RU. etc.) tothe first STA, and may allocate the second RU (e.g., 26/52/106/242-RU,etc.) to the second STA. That is, the transmitting STA (e.g., AP) maytransmit HE-STF, HE-LTF, and Data fields for the first STA through thefirst RU in one MU PPDU, and may transmit HE-STF, HE-LTF, and Datafields for the second STA through the second RU.

Information related to a layout of the RU may be signaled throughHE-SIG-B.

FIG. 8 illustrates a structure of an HE-SIG-B field.

As illustrated, an HE-SIG-B field 810 includes a common field 820 and auser-specific field 830. The common field 820 may include informationcommonly applied to all users (i.e., user STAs) which receive SIG-B. Theuser-specific field 830 may be called a user-specific control field.When the SIG-B is transferred to a plurality of users, the user-specificfield 830 may be applied only any one of the plurality of users.

As illustrated in FIG. 8 , the common field 820 and the user-specificfield 830 may be separately encoded.

The common field 820 may include RU allocation information of N*8 bits.For example, the RU allocation information may include informationrelated to a location of an RU. For example, when a 20 MHz channel isused as shown in FIG. 5 , the RU allocation information may includeinformation related to a specific frequency band to which a specific RU(26-RU/52-RU/106-RU) is arranged.

An example of a case in which the RU allocation information consists of8 bits is as follows.

TABLE 1 8 bits indices (B7 B6 B5 B4 Number B3 B2 B1 B0) #1 #2 #3 #4 #5#6 #7 #8 #9 of entries 00000000 26 26 26 26 26 26 26 26 26 1 00000001 2626 26 26 26 26 26 52 1 00000010 26 26 26 26 26 52 26 26 1 00000011 26 2626 26 26 52 52 1 00000100 26 26 52 26 26 26 26 26 1 00000101 26 26 52 2626 26 52 1 00000110 26 26 52 26 52 26 26 1 00000111 26 26 52 26 52 52 100001000 52 26 26 26 26 26 26 26 1

As shown the example of FIG. 5 , up to nine 26-RUs may be allocated tothe 20 MHz channel. When the RU allocation information of the commonfield 820 is set to “00000000” as shown in Table 1, the nine 26-RUs maybe allocated to a corresponding channel (i.e., 20 MHz). In addition,when the RU allocation information of the common field 820 is set to“00000001” as shown in Table 1, seven 26-RUs and one 52-RU are arrangedin a corresponding channel That is, in the example of FIG. 5 , the 52-RUmay be allocated to the rightmost side, and the seven 26-RUs may beallocated to the left thereof.

The example of Table 1 shows only some of RU locations capable ofdisplaying the RU allocation information.

For example, the RU allocation information may include an example ofTable 2 below.

TABLE 2 8 bits indices (B7 B6 B5 B4 Number B3 B2 B1 B0) #1 #2 #3 #4 #5#6 #7 #8 #9 of entries 01000y₂y₁y₀ 106 26 26 26 26 26 8 01001y₂y₁y₀ 10626 26 26 52 8

“01000y2y1y0” relates to an example in which a 106-RU is allocated tothe leftmost side of the 20 MHz channel, and five 26-RUs are allocatedto the right side thereof. In this case, a plurality of STAs (e.g.,user-STAs) may be allocated to the 106-RU, based on a MU-MIMO scheme.Specifically, up to 8 STAs (e.g., user-STAs) may be allocated to the106-RU, and the number of STAs (e.g., user-STAs) allocated to the 106-RUis determined based on 3-bit information (y2y1y0). For example, when the3-bit information (y2y1y0) is set to N, the number of STAs (e.g.,user-STAs) allocated to the 106-RU based on the MU-MIMO scheme may beN+1.

In general, a plurality of STAs (e.g., user STAs) different from eachother may be allocated to a plurality of RUs. However, the plurality ofSTAs (e.g., user STAs) may be allocated to one or more RUs having atleast a specific size (e.g., 106 subcarriers), based on the MU-MIMOscheme.

As shown in FIG. 8 , the user-specific field 830 may include a pluralityof user fields. As described above, the number of STAs (e.g., user STAs)allocated to a specific channel may be determined based on the RUallocation information of the common field 820. For example, when the RUallocation information of the common field 820 is “00000000”, one userSTA may be allocated to each of nine 26-RUs (e.g., nine user STAs may beallocated). That is, up to 9 user STAs may be allocated to a specificchannel through an OFDMA scheme. In other words, up to 9 user STAs maybe allocated to a specific channel through a non-MU-MIMO scheme.

For example, when RU allocation is set to “01000y2y1y0”, a plurality ofSTAs may be allocated to the 106-RU arranged at the leftmost sidethrough the MU-MIMO scheme, and five user STAs may be allocated to five26-RUs arranged to the right side thereof through the non-MU MIMOscheme. This case is specified through an example of FIG. 9 .

FIG. 9 illustrates an example in which a plurality of user STAs areallocated to the same RU through a MU-MIMO scheme.

For example, when RU allocation is set to “01000010” as shown in FIG. 9, a 106-RU may be allocated to the leftmost side of a specific channel,and five 26-RUs may be allocated to the right side thereof. In addition,three user STAs may be allocated to the 106-RU through the MU-MIMOscheme. As a result, since eight user STAs are allocated, theuser-specific field 830 of HE-SIG-B may include eight user fields.

The eight user fields may be expressed in the order shown in FIG. 9 . Inaddition, as shown in FIG. 8 , two user fields may be implemented withone user block field.

The user fields shown in FIG. 8 and FIG. 9 may be configured based ontwo formats. That is, a user field related to a MU-MIMO scheme may beconfigured in a first format, and a user field related to a non-MIMOscheme may be configured in a second format. Referring to the example ofFIG. 9 , a user field 1 to a user field 3 may be based on the firstformat, and a user field 4 to a user field 8 may be based on the secondformat. The first format or the second format may include bitinformation of the same length (e.g., 21 bits).

Each user field may have the same size (e.g., 21 bits). For example, theuser field of the first format (the first of the MU-MIMO scheme) may beconfigured as follows.

For example, a first bit (i.e., B0-B10) in the user field (i.e., 21bits) may include identification information (e.g., STA-ID, partial AID,etc.) of a user STA to which a corresponding user field is allocated. Inaddition, a second bit (i.e., B11-B14) in the user field (i.e., 21 bits)may include information related to a spatial configuration.Specifically, an example of the second bit (i.e., B11-B14) may be asshown in Table 3 and Table 4 below.

TABLE 3 N_(STS) N_(STS) N_(STS) N_(STS) N_(STS) N_(STS) N_(STS) N_(STS)Total Number N_(user) B3 . . . B0 [1] [2] [3] [4] [5] [6] [7] [8]N_(STS) of entries 2 0000-0011 1-4 1 2-5 10 0100-0110 2-4 2 4-60111-1000 3-4 3 6-7 1001 4 4 8 3 0000-0011 1-4 1 1 3-6 13 0100-0110 2-42 1 5-7 0111-1000 3-4 3 1 7-8 1001-1011 2-4 2 2 6-8 1100 3 3 2 8 40000-0011 1-4 1 1 1 4-7 11 0100-0110 2-4 2 1 1 6-8 0111 3 3 1 1 81000-1001 2-3 2 2 1 7-8 1010 2 2 2 2 8

TABLE 4 N_(STS) N_(STS) N_(STS) N_(STS) N_(STS) N_(STS) N_(STS) N_(STS)Total Number N_(user) B3 . . . B0 [1] [2] [3] [4] [5] [6] [7] [8]N_(STS) of entries 5 0000-0011 1-4 1 1 1 1 5-8 7 0100-0101 2-3 2 1 1 17-8 0110 2 2 2 1 1 8 6 0000-0010 1-3 1 1 1 1 1 6-8 4 0011 2 2 1 1 1 1 87 0000-0001 1-2 1 1 1 1 1 1 7-8 2 8 0000 1 1 1 1 1 1 1 1 8 1

As shown in Table 3 and/or Table 4, the second bit (e.g., B11-B14) mayinclude information related to the number of spatial streams allocatedto the plurality of user STAs which are allocated based on the MU-MIMOscheme. For example, when three user STAs are allocated to the 106-RUbased on the MU-MIMO scheme as shown in FIG. 9 , N_user is set to “3”.Therefore, values of N_STS[1], N_STS[2], and N_STS[3] may be determinedas shown in Table 3. For example, when a value of the second bit(B11-B14) is “0011”, it may be set to N_STS[1]=4, N_STS[2]=1,N_STS[3]=1. That is, in the example of FIG. 9 , four spatial streams maybe allocated to the user field 1, one spatial stream may be allocated tothe user field 1, and one spatial stream may be allocated to the userfield 3.

As shown in the example of Table 3 and/or Table 4, information (i.e.,the second bit, B11-B14) related to the number of spatial streams forthe user STA may consist of 4 bits. In addition, the information (i.e.,the second bit, B11-B14) on the number of spatial streams for the userSTA may support up to eight spatial streams. In addition, theinformation (i.e., the second bit, B11-B14) on the number of spatialstreams for the user STA may support up to four spatial streams for oneuser STA.

In addition, a third bit (i.e., B15-18) in the user field (i.e., 21bits) may include modulation and coding scheme (MCS) information. TheMCS information may be applied to a data field in a PPDU includingcorresponding SIG-B.

An MCS, MCS information, an MCS index, an MCS field, or the like used inthe present specification may be indicated by an index value. Forexample, the MCS information may be indicated by an index 0 to an index11. The MCS information may include information related to aconstellation modulation type (e.g., BPSK, QPSK, 16-QAM, 64-QAM,256-QAM, 1024-QAM, etc.) and information related to a coding rate (e.g.,1/2, 2/3, 3/4, 5/6e, etc.). Information related to a channel coding type(e.g., LCC or LDPC) may be excluded in the MCS information.

In addition, a fourth bit (i.e., B19) in the user field (i.e., 21 bits)may be a reserved field.

In addition, a fifth bit (i.e., B20) in the user field (i.e., 21 bits)may include information related to a coding type (e.g., BCC or LDPC).That is, the fifth bit (i.e., B20) may include information related to atype (e.g., BCC or LDPC) of channel coding applied to the data field inthe PPDU including the corresponding SIG-B.

The aforementioned example relates to the user field of the first format(the format of the MU-MIMO scheme). An example of the user field of thesecond format (the format of the non-MU-MIMO scheme) is as follows.

A first bit (e.g., B0-B10) in the user field of the second format mayinclude identification information of a user STA. In addition, a secondbit (e.g., B11-B13) in the user field of the second format may includeinformation related to the number of spatial streams applied to acorresponding RU. In addition, a third bit (e.g., B14) in the user fieldof the second format may include information related to whether abeamforming steering matrix is applied. A fourth bit (e.g., B15-B18) inthe user field of the second format may include modulation and codingscheme (MCS) information. In addition, a fifth bit (e.g., B19) in theuser field of the second format may include information related towhether dual carrier modulation (DCM) is applied. In addition, a sixthbit (i.e., B20) in the user field of the second format may includeinformation related to a coding type (e.g., BCC or LDPC).

FIG. 10 illustrates an operation based on UL-MU. As illustrated, atransmitting STA (e.g., an AP) may perform channel access throughcontending (e.g., a backoff operation), and may transmit a trigger frame1030. That is, the transmitting STA may transmit a PPDU including thetrigger frame 1030. Upon receiving the PPDU including the trigger frame,a trigger-based (TB) PPDU is transmitted after a delay corresponding toSIFS.

TB PPDUs 1041 and 1042 may be transmitted at the same time period, andmay be transmitted from a plurality of STAs (e.g., user STAs) havingAIDs indicated in the trigger frame 1030. An ACK frame 1050 for the TBPPDU may be implemented in various forms.

A specific feature of the trigger frame is described with reference toFIG. 11 to FIG. 13 . Even if UL-MU communication is used, an orthogonalfrequency division multiple access (OFDMA) scheme or a MU MIMO schememay be used, and the OFDMA and MU-MIMO schemes may be simultaneouslyused.

FIG. 11 illustrates an example of a trigger frame. The trigger frame ofFIG. 11 allocates a resource for uplink multiple-user (MU) transmission,and may be transmitted, for example, from an AP. The trigger frame maybe configured of a MAC frame, and may be included in a PPDU.

Each field shown in FIG. 11 may be partially omitted, and another fieldmay be added. In addition, a length of each field may be changed to bedifferent from that shown in the figure.

A frame control field 1110 of FIG. 11 may include information related toa MAC protocol version and extra additional control information. Aduration field 1120 may include time information for NAV configurationor information related to an identifier (e.g., AID) of a STA.

In addition, an RA field 1130 may include address information of areceiving STA of a corresponding trigger frame, and may be optionallyomitted. A TA field 1140 may include address information of a STA (e.g.,an AP) which transmits the corresponding trigger frame. A commoninformation field 1150 includes common control information applied tothe receiving STA which receives the corresponding trigger frame. Forexample, a field indicating a length of an L-SIG field of an uplink PPDUtransmitted in response to the corresponding trigger frame orinformation for controlling content of a SIG-A field (i.e., HE-SIG-Afield) of the uplink PPDU transmitted in response to the correspondingtrigger frame may be included. In addition, as common controlinformation, information related to a length of a CP of the uplink PPDUtransmitted in response to the corresponding trigger frame orinformation related to a length of an LTF field may be included.

In addition, per user information fields 1160#1 to 1160#N correspondingto the number of receiving STAs which receive the trigger frame of FIG.11 are preferably included. The per user information field may also becalled an “allocation field”.

In addition, the trigger frame of FIG. 11 may include a padding field1170 and a frame check sequence field 1180.

Each of the per user information fields 1160#1 to 1160#N shown in FIG.11 may include a plurality of subfields.

FIG. 12 illustrates an example of a common information field of atrigger frame. A subfield of FIG. 12 may be partially omitted, and anextra subfield may be added. In addition, a length of each subfieldillustrated may be changed.

A length field 1210 illustrated has the same value as a length field ofan L-SIG field of an uplink PPDU transmitted in response to acorresponding trigger frame, and a length field of the L-SIG field ofthe uplink PPDU indicates a length of the uplink PPDU. As a result, thelength field 1210 of the trigger frame may be used to indicate thelength of the corresponding uplink PPDU.

In addition, a cascade identifier field 1220 indicates whether a cascadeoperation is performed. The cascade operation implies that downlink MUtransmission and uplink MU transmission are performed together in thesame TXOP. That is, it implies that downlink MU transmission isperformed and thereafter uplink MU transmission is performed after apre-set time (e.g., SIFS). During the cascade operation, only onetransmitting device (e.g., AP) may perform downlink communication, and aplurality of transmitting devices (e.g., non-APs) may perform uplinkcommunication.

A CS request field 1230 indicates whether a wireless medium state or aNAV or the like is necessarily considered in a situation where areceiving device which has received a corresponding trigger frametransmits a corresponding uplink PPDU.

An HE-SIG-A information field 1240 may include information forcontrolling content of a SIG-A field (i.e., HE-SIG-A field) of theuplink PPDU in response to the corresponding trigger frame.

A CP and LTF type field 1250 may include information related to a CPlength and LTF length of the uplink PPDU transmitted in response to thecorresponding trigger frame. A trigger type field 1260 may indicate apurpose of using the corresponding trigger frame, for example, typicaltriggering, triggering for beamforming, a request for block ACK/NACK, orthe like.

It may be assumed that the trigger type field 1260 of the trigger framein the present specification indicates a trigger frame of a basic typefor typical triggering. For example, the trigger frame of the basic typemay be referred to as a basic trigger frame.

FIG. 13 illustrates an example of a subfield included in a per userinformation field. A user information field 1300 of FIG. 13 may beunderstood as any one of the per user information fields 1160#1 to1160#N mentioned above with reference to FIG. 11 . A subfield includedin the user information field 1300 of FIG. 13 may be partially omitted,and an extra subfield may be added. In addition, a length of eachsubfield illustrated may be changed.

A user identifier field 1310 of FIG. 13 indicates an identifier of a STA(i.e., receiving STA) corresponding to per user information. An exampleof the identifier may be the entirety or part of an associationidentifier (AID) value of the receiving STA.

In addition, an RU allocation field 1320 may be included. That is, whenthe receiving STA identified through the user identifier field 1310transmits a TB PPDU in response to the trigger frame, the TB PPDU istransmitted through an RU indicated by the RU allocation field 1320. Inthis case, the RU indicated by the RU allocation field 1320 may be an RUshown in FIG. 5 , FIG. 6 , and FIG. 7 .

The subfield of FIG. 13 may include a coding type field 1330. The codingtype field 1330 may indicate a coding type of the TB PPDU. For example,when BCC coding is applied to the TB PPDU, the coding type field 1330may be set to ‘1’, and when LDPC coding is applied, the coding typefield 1330 may be set to ‘0’.

In addition, the subfield of FIG. 13 may include an MCS field 1340. TheMCS field 1340 may indicate an MCS scheme applied to the TB PPDU. Forexample, when BCC coding is applied to the TB PPDU, the coding typefield 1330 may be set to ‘1’, and when LDPC coding is applied, thecoding type field 1330 may be set to ‘0’.

Hereinafter, a UL OFDMA-based random access (UORA) scheme will bedescribed.

FIG. 14 describes a technical feature of the UORA scheme.

A transmitting STA (e.g., an AP) may allocate six RU resources through atrigger frame as shown in FIG. 14 . Specifically, the AP may allocate a1st RU resource (AID 0, RU 1), a 2nd RU resource (AID 0, RU 2), a 3rd RUresource (AID 0, RU 3), a 4th RU resource (AID 2045, RU 4), a 5th RUresource (AID 2045, RU 5), and a 6th RU resource (AID 3, RU 6).Information related to the AID 0, AID 3, or AID 2045 may be included,for example, in the user identifier field 1310 of FIG. 13 . Informationrelated to the RU 1 to RU 6 may be included, for example, in the RUallocation field 1320 of FIG. 13 . AID=0 may imply a UORA resource foran associated STA, and AID=2045 may imply a UORA resource for anun-associated STA. Accordingly, the 1st to 3rd RU resources of FIG. 14may be used as a UORA resource for the associated STA, the 4th and 5thRU resources of FIG. 14 may be used as a UORA resource for theun-associated STA, and the 6th RU resource of FIG. 14 may be used as atypical resource for UL MU.

In the example of FIG. 14 , an OFDMA random access backoff (OBO) of aSTA1 is decreased to 0, and the STA1 randomly selects the 2nd RUresource (AID 0, RU 2). In addition, since an OBO counter of a STA2/3 isgreater than 0, an uplink resource is not allocated to the STA2/3. Inaddition, regarding a STA4 in FIG. 14 , since an AID (e.g., AID=3) ofthe STA4 is included in a trigger frame, a resource of the RU 6 isallocated without backoff.

Specifically, since the STA1 of FIG. 14 is an associated STA, the totalnumber of eligible RA RUs for the STA1 is 3 (RU 1, RU 2, and RU 3), andthus the STA1 decreases an OBO counter by 3 so that the OBO counterbecomes 0. In addition, since the STA2 of FIG. 14 is an associated STA,the total number of eligible RA RUs for the STA2 is 3 (RU 1, RU 2, andRU 3), and thus the STA2 decreases the OBO counter by 3 but the OBOcounter is greater than 0. In addition, since the STA3 of FIG. 14 is anun-associated STA, the total number of eligible RA RUs for the STA3 is 2(RU 4, RU 5), and thus the STA3 decreases the OBO counter by 2 but theOBO counter is greater than 0.

FIG. 15 illustrates an example of a channel used/supported/definedwithin a 2.4 GHz band.

The 2.4 GHz band may be called in other terms such as a first band. Inaddition, the 2.4 GHz band may imply a frequency domain in whichchannels of which a center frequency is close to 2.4 GHz (e.g., channelsof which a center frequency is located within 2.4 to 2.5 GHz) areused/supported/defined.

A plurality of 20 MHz channels may be included in the 2.4 GHz band. 20MHz within the 2.4 GHz may have a plurality of channel indices (e.g., anindex 1 to an index 14). For example, a center frequency of a 20 MHzchannel to which a channel index 1 is allocated may be 2.412 GHz, acenter frequency of a 20 MHz channel to which a channel index 2 isallocated may be 2.417 GHz, and a center frequency of a 20 MHz channelto which a channel index N is allocated may be (2.407+0.005*N) GHz. Thechannel index may be called in various terms such as a channel number orthe like. Specific numerical values of the channel index and centerfrequency may be changed.

FIG. 15 exemplifies 4 channels within a 2.4 GHz band. Each of 1st to 4thfrequency domains 1510 to 1540 shown herein may include one channel. Forexample, the 1st frequency domain 1510 may include a channel 1 (a 20 MHzchannel having an index 1). In this case, a center frequency of thechannel 1 may be set to 2412 MHz. The 2nd frequency domain 1520 mayinclude a channel 6. In this case, a center frequency of the channel 6may be set to 2437 MHz. The 3rd frequency domain 1530 may include achannel 11. In this case, a center frequency of the channel 11 may beset to 2462 MHz. The 4th frequency domain 1540 may include a channel 14.In this case, a center frequency of the channel 14 may be set to 2484MHz.

FIG. 16 illustrates an example of a channel used/supported/definedwithin a 5 GHz band.

The 5 GHz band may be called in other terms such as a second band or thelike. The 5 GHz band may imply a frequency domain in which channels ofwhich a center frequency is greater than or equal to 5 GHz and less than6 GHz (or less than 5.9 GHz) are used/supported/defined. Alternatively,the 5 GHz band may include a plurality of channels between 4.5 GHz and5.5 GHz. A specific numerical value shown in FIG. 16 may be changed.

A plurality of channels within the 5 GHz band include an unlicensednational information infrastructure (UNII)-1, a UNII-2, a UNII-3, and anISM. The INII-1 may be called UNII Low. The UNII-2 may include afrequency domain called UNII Mid and UNII-2Extended. The UNII-3 may becalled UNII-Upper.

A plurality of channels may be configured within the 5 GHz band, and abandwidth of each channel may be variously set to, for example, 20 MHz,40 MHz, 80 MHz, 160 MHz, or the like. For example, 5170 MHz to 5330 MHzfrequency domains/ranges within the UNII-1 and UNII-2 may be dividedinto eight 20 MHz channels. The 5170 MHz to 5330 MHz frequencydomains/ranges may be divided into four channels through a 40 MHzfrequency domain. The 5170 MHz to 5330 MHz frequency domains/ranges maybe divided into two channels through an 80 MHz frequency domain.Alternatively, the 5170 MHz to 5330 MHz frequency domains/ranges may bedivided into one channel through a 160 MHz frequency domain.

FIG. 17 illustrates an example of a channel used/supported/definedwithin a 6 GHz band.

The 6 GHz band may be called in other terms such as a third band or thelike. The 6 GHz band may imply a frequency domain in which channels ofwhich a center frequency is greater than or equal to 5.9 GHz areused/supported/defined. A specific numerical value shown in FIG. 17 maybe changed.

For example, the 20 MHz channel of FIG. 17 may be defined starting from5.940 GHz. Specifically, among 20 MHz channels of FIG. 17 , the leftmostchannel may have an index 1 (or a channel index, a channel number,etc.), and 5.945 GHz may be assigned as a center frequency. That is, acenter frequency of a channel of an index N may be determined as(5.940+0.005*N) GHz.

Accordingly, an index (or channel number) of the 2 MHz channel of FIG.17 may be 1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45, 49, 53, 57, 61,65, 69, 73, 77, 81, 85, 89, 93, 97, 101, 105, 109, 113, 117, 121, 125,129, 133, 137, 141, 145, 149, 153, 157, 161, 165, 169, 173, 177, 181,185, 189, 193, 197, 201, 205, 209, 213, 217, 221, 225, 229, 233. Inaddition, according to the aforementioned (5.940+0.005*N)GHz rule, anindex of the 40 MHz channel of FIG. 17 may be 3, 11, 19, 27, 35, 43, 51,59, 67, 75, 83, 91, 99, 107, 115, 123, 131, 139, 147, 155, 163, 171,179, 187, 195, 203, 211, 219, 227.

Although 20, 40, 80, and 160 MHz channels are illustrated in the exampleof FIG. 17 , a 240 MHz channel or a 320 MHz channel may be additionallyadded.

Hereinafter, a PPDU transmitted/received in a STA of the presentspecification will be described.

FIG. 18 illustrates an example of a PPDU used in the presentspecification.

The PPDU of FIG. 18 may be called in various terms such as an EHT PPDU,a TX PPDU, an RX PPDU, a first type or N-th type PPDU, or the like. Forexample, in the present specification, the PPDU or the EHT PPDU may becalled in various terms such as a TX PPDU, a RX PPDU, a first type orN-th type PPDU, or the like. In addition, the EHT PPDU may be used in anEHT system and/or a new WLAN system enhanced from the EHT system.

The PPDU of FIG. 18 may indicate the entirety or part of a PPDU typeused in the EHT system. For example, the example of FIG. 18 may be usedfor both of a single-user (SU) mode and a multi-user (MU) mode. In otherwords, the PPDU of FIG. 18 may be a PPDU for one receiving STA or aplurality of receiving STAs. When the PPDU of FIG. 18 is used for atrigger-based (TB) mode, the EHT-SIG of FIG. 18 may be omitted. In otherwords, a STA which has received a trigger frame for uplink-MU (UL-MU)may transmit the PPDU in which the EHT-SIG is omitted in the example ofFIG. 18 .

In FIG. 18 , an L-STF to an EHT-LTF may be called a preamble or aphysical preamble, and may begenerated/transmitted/received/obtained/decoded in a physical layer.

A subcarrier spacing of the L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, andEHT-SIG fields of FIG. 18 may be determined as 312.5 kHz, and asubcarrier spacing of the EHT-STF, EHT-LTF, and Data fields may bedetermined as 78.125 kHz. That is, a tone index (or subcarrier index) ofthe L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, and EHT-SIG fields may beexpressed in unit of 312.5 kHz, and a tone index (or subcarrier index)of the EHT-STF, EHT-LTF, and Data fields may be expressed in unit of78.125 kHz.

In the PPDU of FIG. 18 , the L-LTE and the L-STF may be the same asthose in the conventional fields.

The L-SIG field of FIG. 18 may include, for example, bit information of24 bits. For example, the 24-bit information may include a rate field of4 bits, a reserved bit of 1 bit, a length field of 12 bits, a parity bitof 1 bit, and a tail bit of 6 bits. For example, the length field of 12bits may include information related to a length or time duration of aPPDU. For example, the length field of 12 bits may be determined basedon a type of the PPDU. For example, when the PPDU is a non-HT, HT, VHTPPDU or an EHT PPDU, a value of the length field may be determined as amultiple of 3. For example, when the PPDU is an HE PPDU, the value ofthe length field may be determined as “a multiple of 3”+1 or “a multipleof 3”+2. In other words, for the non-HT, HT, VHT PPDI or the EHT PPDU,the value of the length field may be determined as a multiple of 3, andfor the HE PPDU, the value of the length field may be determined as “amultiple of 3”+1 or “a multiple of 3”+2.

For example, the transmitting STA may apply BCC encoding based on a 1/2coding rate to the 24-bit information of the L-SIG field. Thereafter,the transmitting STA may obtain a BCC coding bit of 48 bits. BPSKmodulation may be applied to the 48-bit coding bit, thereby generating48 BPSK symbols. The transmitting STA may map the 48 BPSK symbols topositions except for a pilot subcarrier{subcarrier index −21, −7, +7,+21} and a DC subcarrier{subcarrier index 0}. As a result, the 48 BPSKsymbols may be mapped to subcarrier indices −26 to −22, −20 to −8, −6 to−1, +1 to +6, +8 to +20, and +22 to +26. The transmitting STA mayadditionally map a signal of {−1, −1, −1, 1} to a subcarrier index{−28,−27, +27, +28}. The aforementioned signal may be used for channelestimation on a frequency domain corresponding to −28, −27, +27, +281.

The transmitting STA may generate an RL-SIG generated in the same manneras the L-SIG. BPSK modulation may be applied to the RL-SIG. Thereceiving STA may know that the RX PPDU is the HE PPDU or the EHT PPDU,based on the presence of the RL-SIG.

A universal SIG (U-SIG) may be inserted after the RL-SIG of FIG. 18 .The U-SIB may be called in various terms such as a first SIG field, afirst SIG, a first type SIG, a control signal, a control signal field, afirst (type) control signal, or the like.

The U-SIG may include information of N bits, and may include informationfor identifying a type of the EHT PPDU. For example, the U-SIG may beconfigured based on two symbols (e.g., two contiguous OFDM symbols).Each symbol (e.g., OFDM symbol) for the U-SIG may have a duration of 4us. Each symbol of the U-SIG may be used to transmit the 26-bitinformation. For example, each symbol of the U-SIG may betransmitted/received based on 52 data tomes and 4 pilot tones.

Through the U-SIG (or U-SIG field), for example, A-bit information(e.g., 52 un-coded bits) may be transmitted. A first symbol of the U-SIGmay transmit first X-bit information (e.g., 26 un-coded bits) of theA-bit information, and a second symbol of the U-SIB may transmit theremaining Y-bit information (e.g., 26 un-coded bits) of the A-bitinformation. For example, the transmitting STA may obtain 26 un-codedbits included in each U-SIG symbol. The transmitting STA may performconvolutional encoding (i.e., BCC encoding) based on a rate of R=1/2 togenerate 52-coded bits, and may perform interleaving on the 52-codedbits. The transmitting STA may perform BPSK modulation on theinterleaved 52-coded bits to generate 52 BPSK symbols to be allocated toeach U-SIG symbol. One U-SIG symbol may be transmitted based on 65 tones(subcarriers) from a subcarrier index −28 to a subcarrier index +28,except for a DC index 0. The 52 BPSK symbols generated by thetransmitting STA may be transmitted based on the remaining tones(subcarriers) except for pilot tones, i.e., tones −21, −7, +7, +21.

For example, the A-bit information (e.g., 52 un-coded bits) generated bythe U-SIG may include a CRC field (e.g., a field having a length of 4bits) and a tail field (e.g., a field having a length of 6 bits). TheCRC field and the tail field may be transmitted through the secondsymbol of the U-SIG. The CRC field may be generated based on 26 bitsallocated to the first symbol of the U-SIG and the remaining 16 bitsexcept for the CRC/tail fields in the second symbol, and may begenerated based on the conventional CRC calculation algorithm. Inaddition, the tail field may be used to terminate trellis of aconvolutional decoder, and may be set to, for example, “000000”.

The A-bit information (e.g., 52 un-coded bits) transmitted by the U-SIG(or U-SIG field) may be divided into version-independent bits andversion-dependent bits. For example, the version-independent bits mayhave a fixed or variable size. For example, the version-independent bitsmay be allocated only to the first symbol of the U-SIG, or theversion-independent bits may be allocated to both of the first andsecond symbols of the U-SIG. For example, the version-independent bitsand the version-dependent bits may be called in various terms such as afirst control bit, a second control bit, or the like.

For example, the version-independent bits of the U-SIG may include a PHYversion identifier of 3 bits. For example, the PHY version identifier of3 bits may include information related to a PHY version of a TX/RX PPDU.For example, a first value of the PHY version identifier of 3 bits mayindicate that the TX/RX PPDU is an EHT PPDU. In other words, when thetransmitting STA transmits the EHT PPDU, the PHY version identifier of 3bits may be set to a first value. In other words, the receiving STA maydetermine that the RX PPDU is the EHT PPDU, based on the PHY versionidentifier having the first value.

For example, the version-independent bits of the U-SIG may include aUL/DL flag field of 1 bit. A first value of the UL/DL flag field of 1bit relates to UL communication, and a second value of the UL/DL flagfield relates to DL communication.

For example, the version-independent bits of the U-SIG may includeinformation related to a TXOP length and information related to a BSScolor ID.

For example, when the EHT PPDU is divided into various types (e.g.,various types such as an EHT PPDU related to an SU mode, an EHT PPDUrelated to a MU mode, an EHT PPDU related to a TB mode, an EHT PPDUrelated to extended range transmission, or the like), informationrelated to the type of the EHT PPDU may be included in theversion-dependent bits of the U-SIG.

For example, the U-SIG may include: 1) a bandwidth field includinginformation related to a bandwidth; 2) a field including informationrelated to an MCS scheme applied to EHT-SIG; 3) an indication fieldincluding information regarding whether a dual subcarrier modulation(DCM) scheme is applied to EHT-SIG; 4) a field including informationrelated to the number of symbol used for EHT-SIG; 5) a field includinginformation regarding whether the EHT-SIG is generated across a fullband; 6) a field including information related to a type of EHT-LTF/STF;and 7) information related to a field indicating an EHT-LTF length and aCP length.

Preamble puncturing may be applied to the PPDU of FIG. 18 . The preamblepuncturing implies that puncturing is applied to part (e.g., a secondary20 MHz band) of the full band. For example, when an 80 MHz PPDU istransmitted, a STA may apply puncturing to the secondary 20 MHz band outof the 80 MHz band, and may transmit a PPDU only through a primary 20MHz band and a secondary 40 MHz band.

For example, a pattern of the preamble puncturing may be configured inadvance. For example, when a first puncturing pattern is applied,puncturing may be applied only to the secondary 20 MHz band within the80 MHz band. For example, when a second puncturing pattern is applied,puncturing may be applied to only any one of two secondary 20 MHz bandsincluded in the secondary 40 MHz band within the 80 MHz band. Forexample, when a third puncturing pattern is applied, puncturing may beapplied to only the secondary 20 MHz band included in the primary 80 MHzband within the 160 MHz band (or 80+80 MHz band). For example, when afourth puncturing is applied, puncturing may be applied to at least one20 MHz channel not belonging to a primary 40 MHz band in the presence ofthe primary 40 MHz band included in the 80 MHz band within the 160 MHzband (or 80+80 MHz band).

Information related to the preamble puncturing applied to the PPDU maybe included in U-SIG and/or EHT-SIG. For example, a first field of theU-SIG may include information related to a contiguous bandwidth, andsecond field of the U-SIG may include information related to thepreamble puncturing applied to the PPDU.

For example, the U-SIG and the EHT-SIG may include the informationrelated to the preamble puncturing, based on the following method. Whena bandwidth of the PPDU exceeds 80 MHz, the U-SIG may be configuredindividually in unit of 80 MHz. For example, when the bandwidth of thePPDU is 160 MHz, the PPDU may include a first U-SIG for a first 80 MHzband and a second U-SIG for a second 80 MHz band. In this case, a firstfield of the first U-SIG may include information related to a 160 MHzbandwidth, and a second field of the first U-SIG may include informationrelated to a preamble puncturing (i.e., information related to apreamble puncturing pattern) applied to the first 80 MHz band. Inaddition, a first field of the second U-SIG may include informationrelated to a 160 MHz bandwidth, and a second field of the second U-SIGmay include information related to a preamble puncturing (i.e.,information related to a preamble puncturing pattern) applied to thesecond 80 MHz band. Meanwhile, an EHT-SIG contiguous to the first U-SIGmay include information related to a preamble puncturing applied to thesecond 80 MHz band (i.e., information related to a preamble puncturingpattern), and an EHT-SIG contiguous to the second U-SIG may includeinformation related to a preamble puncturing (i.e., information relatedto a preamble puncturing pattern) applied to the first 80 MHz band.

Additionally or alternatively, the U-SIG and the EHT-SIG may include theinformation related to the preamble puncturing, based on the followingmethod. The U-SIG may include information related to a preamblepuncturing (i.e., information related to a preamble puncturing pattern)for all bands. That is, the EHT-SIG may not include the informationrelated to the preamble puncturing, and only the U-SIG may include theinformation related to the preamble puncturing (i.e., the informationrelated to the preamble puncturing pattern).

The U-SIG may be configured in unit of 20 MHz. For example, when an 80MHz PPDU is configured, the U-SIG may be duplicated. That is, fouridentical U-SIGs may be included in the 80 MHz PPDU. PPDUs exceeding an80 MHz bandwidth may include different U-SIGs.

The EHT-SIG of FIG. 18 may include control information for the receivingSTA. The EHT-SIG may be transmitted through at least one symbol, and onesymbol may have a length of 4 us. Information related to the number ofsymbols used for the EHT-SIG may be included in the U-SIG.

The EHT-SIG may include a technical feature of the HE-SIG-B describedwith reference to FIG. 8 and FIG. 9 . For example, the EHT-SIG mayinclude a common field and a user-specific field as in the example ofFIG. 8 . The common field of the EHT-SIG may be omitted, and the numberof user-specific fields may be determined based on the number of users.

As in the example of FIG. 8 , the common field of the EHT-SIG and theuser-specific field of the EHT-SIG may be individually coded. One userblock field included in the user-specific field may include informationfor two users, but a last user block field included in the user-specificfield may include information for one user. That is, one user blockfield of the EHT-SIG may include up to two user fields. As in theexample of FIG. 9 , each user field may be related to MU-MIMOallocation, or may be related to non-MU-MIMO allocation.

As in the example of FIG. 8 , the common field of the EHT-SIG mayinclude a CRC bit and a tail bit. A length of the CRC bit may bedetermined as 4 bits. A length of the tail bit may be determined as 6bits, and may be set to ‘000000’.

As in the example of FIG. 8 , the common field of the EHT-SIG mayinclude RU allocation information. The RU allocation information mayimply information related to a location of an RU to which a plurality ofusers (i.e., a plurality of receiving STAs) are allocated. The RUallocation information may be configured in unit of 8 bits (or N bits),as in Table 1.

The example of Table 5 to Table 7 is an example of 8-bit (or N-bit)information for various RU allocations. An index shown in each table maybe modified, and some entries in Table 5 to Table 7 may be omitted, andentries (not shown) may be added.

The example of Table 5 to Table 7 relates to information related to alocation of an RU allocated to a 20 MHz band. For example, ‘an index 0’of Table 5 may be used in a situation where nine 26-RUs are individuallyallocated (e.g., in a situation where nine 26-RUs shown in FIG. 5 areindividually allocated).

Meanwhile, a plurality or RUs may be allocated to one STA in the EHTsystem. For example, regarding ‘an index 60’ of Table 6, one 26-RU maybe allocated for one user (i.e., receiving STA) to the leftmost side ofthe 20 MHz band, one 26-RU and one 52-RU may be allocated to the rightside thereof, and five 26-RUs may be individually allocated to the rightside thereof.

TABLE 5 Number Indices #1 #2 #3 #4 #5 #6 #7 #8 #9 of entries 0 26 26 2626 26 26 26 26 26 1 1 26 26 26 26 26 26 26 52 1 2 26 26 26 26 26 52 2626 1 3 26 26 26 26 26 52 52 1 4 26 26 52 26 26 26 26 26 1 5 26 26 52 2626 26 52 1 6 26 26 52 26 52 26 26 1 7 26 26 52 26 52 52 1 8 52 26 26 2626 26 26 26 1 9 52 26 26 26 26 26 52 1 10 52 26 26 26 52 26 26 I 11 5226 26 26 52 52 1 12 52 52 26 26 26 26 26 1 13 52 52 26 26 26 52 1 14 5252 26 52 26 26 1 15 52 52 26 52 52 1 16 26 26 26 26 26 106 1 17 26 26 5226 106 1 18 52 26 26 26 106 1 19 52 52 26 106 1

TABLE 6 Number Indices #1 #2 #3 #4 #5 #6 #7 #8 #9 of entries 20 106 2626 26 26 26 1 21 106 26 26 26 52 1 22 106 26 52 26 26 1 23 106 26 52 521 24 52 52 — 52 52 1 25 242-tone RU empty (with zero users) 1 26 106 26106 1 27-34 242 8 35-42 484 8 43-50 996 8 51-58 2*996 8 59 26 26 26 2626 52 + 26 26 1 60 26 26 + 52 26 26 26 26 26 1 61 26 26 + 52 26 26 26 521 62 26 26 + 52 26 52 26 26 1 63 26 26 52 26 52 + 26 26 1 64 26 26 + 5226 52 + 26 26 1 65 26 26 + 52 26 52 52 1

TABLE 7 66 52 26 26 26 52 + 26 26 1 67 52 52 26 52 + 26 26 1 68 52 52 +26 52 52 1 69 26 26 26 26 26 + 106 1 70 26 26 + 52 26 106 1 71 26 26 5226 + 106 1 72 26 26 + 52 26 + 106 1 73 52 26 26 26 + 106 1 74 52 52 26 +106 1 75 106 + 26 26 26 26 26 1 76 106 + 26 26 26 52 1 77 106 + 26 52 2626 1 78 106 26 52 + 26 26 1 79 106 + 26 52 + 26 26 1 80 106 + 26 52 52 181 106 + 26 106 1 82 106 26 + 106 1

A mode in which the common field of the EHT-SIG is omitted may besupported. The mode in which the common field of the EHT-SIG is omittedmay be called a compressed mode. When the compressed mode is used, aplurality of users (i.e., a plurality of receiving STAs) may decode thePPDU (e.g., the data field of the PPDU), based on non-OFDMA. That is,the plurality of users of the EHT PPDU may decode the PPDU (e.g., thedata field of the PPDU) received through the same frequency band.Meanwhile, when a non-compressed mode is used, the plurality of users ofthe EHT PPDU may decode the PPDU (e.g., the data field of the PPDU),based on OFDMA. That is, the plurality of users of the EHT PPDU mayreceive the PPDU (e.g., the data field of the PPDU) through differentfrequency bands.

The EHT-SIG may be configured based on various MCS schemes. As describedabove, information related to an MCS scheme applied to the EHT-SIG maybe included in U-SIG. The EHT-SIG may be configured based on a DCMscheme. For example, among N data tones (e.g., 52 data tones) allocatedfor the EHT-SIG, a first modulation scheme may be applied to half ofcontiguous tones, and a second modulation scheme may be applied to theremaining half of the contiguous tones. That is, a transmitting STA mayuse the first modulation scheme to modulate specific control informationthrough a first symbol and allocate it to half of the contiguous tones,and may use the second modulation scheme to modulate the same controlinformation by using a second symbol and allocate it to the remaininghalf of the contiguous tones. As described above, information (e.g., a1-bit field) regarding whether the DCM scheme is applied to the EHT-SIGmay be included in the U-SIG.

An HE-STF of FIG. 18 may be used for improving automatic gain controlestimation in a multiple input multiple output (MIMO) environment or anOFDMA environment. An HE-LTF of FIG. 18 may be used for estimating achannel in the MIMO environment or the OFDMA environment.

The EHT-STF of FIG. 18 may be set in various types. For example, a firsttype of STF (e.g., 1×STF) may be generated based on a first type STFsequence in which a non-zero coefficient is arranged with an interval of16 subcarriers. An STF signal generated based on the first type STFsequence may have a period of 0.8 μs, and a periodicity signal of 0.8 μsmay be repeated 5 times to become a first type STF having a length of 4μs. For example, a second type of STF (e.g., 2×STF) may be generatedbased on a second type STF sequence in which a non-zero coefficient isarranged with an interval of 8 subcarriers. An STF signal generatedbased on the second type STF sequence may have a period of 1.6 μs, and aperiodicity signal of 1.6 μs may be repeated 5 times to become a secondtype STF having a length of 8 μs. Hereinafter, an example of a sequencefor configuring an EHT-STF (i.e., an EHT-STF sequence) is proposed. Thefollowing sequence may be modified in various ways.

The EHT-STF may be configured based on the following sequence M.

M={−1,−1,−1,1,1,1,−1,1,1,1,−1,1,1,−1,1}  <Equation 1>

The EHT-STF for the 20 MHz PPDU may be configured based on the followingequation. The following example may be a first type (i.e., 1×STF)sequence. For example, the first type sequence may be included in not atrigger-based (TB) PPDU but an EHT-PPDU. In the following equation,(a:b:c) may imply a duration defined as b tone intervals (i.e., asubcarrier interval) from a tone index (i.e., subcarrier index) ‘a’ to atone index ‘c’. For example, the equation 2 below may represent asequence defined as 16 tone intervals from a tone index −112 to a toneindex 112. Since a subcarrier spacing of 78.125 kHz is applied to theEHT-STR, the 16 tone intervals may imply that an EHT-STF coefficient (orelement) is arranged with an interval of 78.125*16=1250 kHz. Inaddition, * implies multiplication, and sqrt( ) implies a square root.In addition, j implies an imaginary number.

EHT-STF(−112:16:112)={M}*(1+j)/sqrt(2)

EHT-STF(0)=0  <Equation 2>

The EHT-STF for the 40 MHz PPDU may be configured based on the followingequation. The following example may be the first type (i.e., 1×STF)sequence.

EHT-STF(−240:16:240)={M,0,−M}*(1+j)/sqrt(2)  <Equation 3>

The EHT-STF for the 80 MHz PPDU may be configured based on the followingequation. The following example may be the first type (i.e., 1×STF)sequence.

EHT-STF(−496:16:496)={M,1,−M,0,−M,1,−M}*(1+j)/sqrt(2)  <Equation 4>

The EHT-STF for the 160 MHz PPDU may be configured based on thefollowing equation. The following example may be the first type (i.e.,1×STF) sequence.

EHT-STF(−1008:16:1008)={M,1,−M,0,−M,1,−M,0,−M,−1,M,0,−M,1,−M}*(1+j)/sqrt(2)  <Equation5>

In the EHT-STF for the 80+80 MHz PPDU, a sequence for lower 80 MHz maybe identical to Equation 4. In the EHT-STF for the 80+80 MHz PPDU, asequence for upper 80 MHz may be configured based on the followingequation.

EHT-STF(−496:16:496)={−M,−1,M,0,−M,1,−M}*(1+j)/sqrt(2)  <Equation 6>

Equation 7 to Equation 11 below relate to an example of a second type(i.e., 2×STF) sequence.

EHT-STF(−120:8:120)={M,0,−M}*(1+j)/sqrt(2)  <Equation 7>

The EHT-STF for the 40 MHz PPDU may be configured based on the followingequation.

EHT-STF(−248:8:248)={M,−1,−M,0,M,−1,M}*(1+j)/sqrt(2)

EHT-STF(−248)=0

EHT-STF(248)=0  <Equation 8>

The EHT-STF for the 80 MHz PPDU may be configured based on the followingequation.

EHT-STF(−504:8:504)={M,−1,M,−1,−M,−1,M,0,−M,1,M,1,−M,1,−M}*(1+j)/sqrt(2)  <Equation9>

The EHT-STF for the 160 MHz PPDU may be configured based on thefollowing equation.

EHT-STF(−1016:16:1016)={M,−1,M,−1,−M,−1,M,0,−M,1,M,1,−M,1,−M,0,−M,1,−M,1,M,1,−M,0,−M,1,M,1,−M,1,−M}*(1+j)/sqrt(2)

EHT-STF(−8)=0, EHT-STF(8)=0,

EHT-STF(−1016)=0, EHT-STF(1016)=0  <Equation 10>

In the EHT-STF for the 80+80 MHz PPDU, a sequence for lower 80 MHz maybe identical to Equation 9. In the EHT-STF for the 80+80 MHz PPDU, asequence for upper 80 MHz may be configured based on the followingequation.

EHT-STF(−504:8:504)={−M,1,−M,1,M,1,−M,0,−M,1,M,1,−M,1,−M}*(1+j)/sqrt(2)

EHT-STF(−504)=0,

EHT-STF(504)=0  <Equation 11>

The EHT-LTF may have first, second, and third types (i.e., 1×, 2×,4×LTF). For example, the first/second/third type LTF may be generatedbased on an LTF sequence in which a non-zero coefficient is arrangedwith an interval of 4/2/1 subcarriers. The first/second/third type LTFmay have a time length of 3.2/6.4/12.8 μs. In addition, a GI (e.g.,0.8/1/6/3.2 μs) having various lengths may be applied to thefirst/second/third type LTF.

Information related to a type of STF and/or LTF (information related toa GI applied to LTF is also included) may be included in a SIG-A fieldand/or SIG-B field or the like of FIG. 18 .

A PPDU (e.g., EHT-PPDU) of FIG. 18 may be configured based on theexample of FIG. 5 and FIG. 6 .

For example, an EHT PPDU transmitted on a 20 MHz band, i.e., a 20 MHzEHT PPDU, may be configured based on the RU of FIG. 5 . That is, alocation of an RU of EHT-STF, EHT-LTF, and data fields included in theEHT PPDU may be determined as shown in FIG. 5 .

An EHT PPDU transmitted on a 40 MHz band, i.e., a 40 MHz EHT PPDU, maybe configured based on the RU of FIG. 6 . That is, a location of an RUof EHT-STF, EHT-LTF, and data fields included in the EHT PPDU may bedetermined as shown in FIG. 6 .

Since the RU location of FIG. 6 corresponds to 40 MHz, a tone-plan for80 MHz may be determined when the pattern of FIG. 6 is repeated twice.That is, an 80 MHz EHT PPDU may be transmitted based on a new tone-planin which not the RU of FIG. 7 but the RU of FIG. 6 is repeated twice.

When the pattern of FIG. 6 is repeated twice, 23 tones (i.e., 11 guardtones+12 guard tones) may be configured in a DC region. That is, atone-plan for an 80 MHz EHT PPDU allocated based on OFDMA may have 23 DCtones. Unlike this, an 80 MHz EHT PPDU allocated based on non-OFDMA(i.e., a non-OFDMA full bandwidth 80 MHz PPDU) may be configured basedon a 996-RU, and may include 5 DC tones, 12 left guard tones, and 11right guard tones.

A tone-plan for 160/240/320 MHz may be configured in such a manner thatthe pattern of FIG. 6 is repeated several times.

The PPDU of FIG. 18 may be determined (or identified) as an EHT PPDUbased on the following method.

A receiving STA may determine a type of an RX PPDU as the EHT PPDU,based on the following aspect. For example, the RX PPDU may bedetermined as the EHT PPDU: 1) when a first symbol after an L-LTF signalof the RX PPDU is a BPSK symbol; 2) when RL-SIG in which the L-SIG ofthe RX PPDU is repeated is detected; and 3) when a result of applying“modulo 3” to a value of a length field of the L-SIG of the RX PPDU isdetected as “0”. When the RX PPDU is determined as the EHT PPDU, thereceiving STA may detect a type of the EHT PPDU (e.g., anSU/MU/Trigger-based/Extended Range type), based on bit informationincluded in a symbol after the RL-SIG of FIG. 18 . In other words, thereceiving STA may determine the RX PPDU as the EHT PPDU, based on: 1) afirst symbol after an L-LTF signal, which is a BPSK symbol; 2) RL-SIGcontiguous to the L-SIG field and identical to L-SIG; 3) L-SIG includinga length field in which a result of applying “modulo 3” is set to “0”;and 4) a 3-bit PHY version identifier of the aforementioned U-SIG (e.g.,a PHY version identifier having a first value).

For example, the receiving STA may determine the type of the RX PPDU asthe EHT PPDU, based on the following aspect. For example, the RX PPDUmay be determined as the HE PPDU: 1) when a first symbol after an L-LTFsignal is a BPSK symbol; 2) when RL-SIG in which the L-SIG is repeatedis detected; and 3) when a result of applying “modulo 3” to a value of alength field of the L-SIG is detected as “1” or “2”.

For example, the receiving STA may determine the type of the RX PPDU asa non-HT, HT, and VHT PPDU, based on the following aspect. For example,the RX PPDU may be determined as the non-HT, HT, and VHT PPDU: 1) when afirst symbol after an L-LTF signal is a BPSK symbol; and 2) when RL-SIGin which L-SIG is repeated is not detected. In addition, even if thereceiving STA detects that the RL-SIG is repeated, when a result ofapplying “modulo 3” to the length value of the L-SIG is detected as “0”,the RX PPDU may be determined as the non-HT, HT, and VHT PPDU.

In the following example, a signal represented as a (TX/RX/UL/DL)signal, a (TX/RX/UL/DL) frame, a (TX/RX/UL/DL) packet, a (TX/RX/UL/DL)data unit, (TX/RX/UL/DL) data, or the like may be a signaltransmitted/received based on the PPDU of FIG. 18 . The PPDU of FIG. 18may be used to transmit/receive frames of various types. For example,the PPDU of FIG. 18 may be used for a control frame. An example of thecontrol frame may include a request to send (RTS), a clear to send(CTS), a power save-poll (PS-poll), BlockACKReq, BlockAck, a null datapacket (NDP) announcement, and a trigger frame. For example, the PPDU ofFIG. 18 may be used for a management frame. An example of the managementframe may include a beacon frame, a (re-)association request frame, a(re-)association response frame, a probe request frame, and a proberesponse frame. For example, the PPDU of FIG. 18 may be used for a dataframe. For example, the PPDU of FIG. 18 may be used to simultaneouslytransmit at least two or more of the control frame, the managementframe, and the data frame.

FIG. 19 illustrates an example of a modified transmission device and/orreceiving device of the present specification.

Each device/STA of the sub-figure (a)/(b) of FIG. 1 may be modified asshown in FIG. 19. A transceiver 630 of FIG. 19 may be identical to thetransceivers 113 and 123 of FIG. 1 . The transceiver 630 of FIG. 19 mayinclude a receiver and a transmitter.

A processor 610 of FIG. 19 may be identical to the processors 111 and121 of FIG. 1 . Alternatively, the processor 610 of FIG. 19 may beidentical to the processing chips 114 and 124 of FIG. 1 .

A memory 620 of FIG. 19 may be identical to the memories 112 and 122 ofFIG. 1 . Alternatively, the memory 620 of FIG. 19 may be a separateexternal memory different from the memories 112 and 122 of FIG. 1 .

Referring to FIG. 19 , a power management module 611 manages power forthe processor 610 and/or the transceiver 630. A battery 612 suppliespower to the power management module 611. A display 613 outputs a resultprocessed by the processor 610. A keypad 614 receives inputs to be usedby the processor 610. The keypad 614 may be displayed on the display613. A SIM card 615 may be an integrated circuit which is used tosecurely store an international mobile subscriber identity (IMSI) andits related key, which are used to identify and authenticate subscriberson mobile telephony devices such as mobile phones and computers.

Referring to FIG. 19 , a speaker 640 may output a result related to asound processed by the processor 610. A microphone 641 may receive aninput related to a sound to be used by the processor 610.

FIG. 20 shows an example of a HE-PPDU.

The illustrated L-STF 2000 may include a short training orthogonalfrequency division multiplexing symbol (OFDM). The L-STF 2000 may beused for frame detection, automatic gain control (AGC), diversitydetection, and coarse frequency/time synchronization.

The L-LTF 2010 may include a long training orthogonal frequency divisionmultiplexing symbol (OFDM). The L-LTF 2010 may be used for finefrequency/time synchronization and channel estimation.

The L-SIG 2020 may be used to transmit control information. The L-SIG2020 may include information related to a data transmission rate and adata length. Also, the L-SIG 2020 may be repeatedly transmitted. Thatis, the L-SIG 2020 may be configured in a repeated format (e.g., may bereferred to as R-LSIG).

The HE-SIG-A 2030 may include control information common to thereceiving station(s).

Specifically, the HE-SIG-A 2030 may include information related to: 1) aDL/UL indicator; 2) a BSS color field that is an identifier of the BSS;3) a field indicating the remaining time of the current TXOPduration/period; 4) a Bandwidth field indicating whether 20, 40, 80,160, 80+80 MHz; 5) a field indicating MCS scheme applied to theHE-SIG-B; 6) an indication field indicating whether modulation dualsubcarrier modulation (DCM) is applied to the HE-SIG-B for MCS; 7) afield indicating the number of symbols used for HE-SIG-B; 8) a fieldindicating whether the HE-SIG-B is generated over the full/entire band;9) a field indicating the number of symbols of the HE-LTF; 10) a fieldindicating a length of the HE-LTF and a CP length; 11) a fieldindicating whether additional OFDM symbols exist for LDPC coding; 12) afield indicating control information on Packet Extension (PE); and/or13) a field indicating information related to a CRC field of theHE-SIG-A, and the like. At least one field of the HE-SIG-A may beomitted or changed. In addition, some fields may be added or omitted inother environments where the HE-SIG-A is not a multi-user (MU)environment.

Also, the HE-SIG-A 2030 may be composed of two parts: HE-SIG-A1 andHE-SIG-A2. The HE-SIG-A1 and HE-SIG-A2 included in the HE-SIG-A may bedefined in the following format structure (field) according to acorresponding PPDU. First, the HE-SIG-A field of the HE SU PPDU may bedefined as follows.

TABLE 8 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionHE-SIG-A1 B0 Format 1 Differentiate an HE SU PPDU and HE ER SU PPDU froman HE TB PPDU: Set to 1 for an HE SU PPDU and HE ER SU PPDU B1 Beam 1Set to 1 to indicate that the pre-HE modulated fields of Change the PPDUare spatially mapped differently from the first symbol of the HE-LTF.Equation (28-6), Equation (28-9), Equation (28-12), Equation (25-14),Equation (28-16) and Equation (28-18) apply if the Bean Change field isset to 1. Set to 0 to indicate that the pre-HE modulated fields of thePPDU are spatially mapped the same way as the first symbol of the HE-LTFon each tone. Equation (28-8), Equation (28-10), Equation (28-13),Equation (28-15), Equation (28-17) and Equation (28-19) apply if theBeam Change field is set to 0 B2 UL/DL 1 Indicates whether the PPDU issent UL ot DL. Set to the value indicated by the TXVECTOR parameterUPLINK_FLAG. B3-B6 MCS 4 For an HE SU PPDU: Set to n for MCSn, where n =0, 1, 2, . . . 11 Values 12-25 are reserved For HE ER SU PPDU withBandwidth field set to 0 (242-tone RU): Set to n for MCSn, where n = 0,1, 2 Values 3-15 are reserved For HE ER SU PPDU with Bandwidth field setto 1 (upper frequency 106-tone RU): Set to 0 for MCS 0 Values 1-15 arereserved

TABLE 9 Two Parts of Number HE-SIG-A Bit Field of bits Description B7DCM 1 Indicates whether or not DCM is applied to the Data field for theMCS indicated. If the STBC field is 0, then set to 1 to indicate thatDCM is applied to the Data field. Neither DCM nor STBC shall be appliedif both the DCM and STBC are set to 1. Set to 0 indicate that DCM is notapplied to the Data field. NOTE-DCM is applied only to HE-MCSs 0, 1, 3and 4. DCM is applied only to 1 and 2 spatial streams. DCM is notapplied in combination with STBC B8-B13 BSS Color 6 The BSS Color fieldis an identifier of the BSS. Set so the value of the TXVECTOR parameterBSS_-COLOR B14 Reserved 1 Reserved and set to 1 B15-B18 Spatial Reuse 4Indicates whether or not spatial reuse is allowed during thetransmission of this PPDU Set to a value from Table 28.21 (Spatial Reusefield encoding for an HE SU PPDU, HE ER SU PPDU, and HE MU PPDU), see27.11.6 (SPATIAL_REUSE). Set to SRP_DISALLOW to prohibit SRP-basedspatial reuse during this PPDU. Set to SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP- based spatial reuse and non-SRGOBSS PD-based spatial reuse during this PPDU. FOR the interpretation ofother values see 27.11.6 (SPATIAL_REUSE) and 27.9 (Spatial reuseoperation). B19-B20 Bandwidth 2 For an HE SU PPDU: Set to 0 for 20 MHzSet to 1 for 40 MHz Set to 2 for 80 MHz Set to 3 for 160 MHz and 80 + 80MHz For an HE ER SU PPDU: set to 0 for 242-tone RU Set to 1 for upperfrequency 106-tone RU within the primary 20 MHz Values 2 and 3 arereserved

TABLE 10 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB21-B22 GI + LTF 2 Indicates the GI duration and HE-LTF size. Size Setto 0 to indicate a 1x HE-LTF and 0.8 μs GI Set to 1 to indicate a 2xHE-LTF and 0.3 μs GI Set to 2 to indicate 3 2x HE-LTF and 1.6 μs GI Setto 3 to indicate: a 4x HE-LTF and 0.8 μs GI if both the DCM and STBCfields are 1. Neither DCM nor STBC shall be applied if both the DCM andSTBC fields ate set to 1. a 4x HE-LTF and 3.2 μs GI, otherwise B23-B25NSTS And 3 If the Doppler field is 0, indicates the number of space-Midamble time streams. Perodicity Set to the number of space-timestreams minus 1 For an HE ER SU PPDU, values 2 to 7 are reserved If theDoppler field is 1, then B23-B24 indicates the number of space timestreams, up to 4, and B25 indicates the midamble periodicity. B23-B24 isset to the number of space time streams minus 1. For an HE ER SU PPDU,values 2 and 3 are reserved B25 is set to 0 if TXVECTOR parameterMIDAMBLE_ PERIODICITY is 10 and set to 1 if TXVECTOR parameterMIDAMBLE_PERIODICITY is 20. HE-SIG-A2 B0-B6 TXOP 7 Set to 127 toindicated no duration information (HE SU if TXVECTOR parameterTXOP_DURATON PPDU) or is set to UXSPECIFIED. HE-SIG-A3 Set to a valueless than 127 to indicate duration information (HE ER SU for NAV settingand protection of the TXOP as PPDU) follows: If TXVECTOR parameterTXOP_DURATION is less than 512, then B0 is set to 0 and B1-B6 is set tofloor(TXOP_DURATION/8) Otherwise, B0 is set to 1 and B1-B6 is set tofloor ((TXOP DURATION-512)/128) where B0 indicates the TXOP lengthgranularity. Set to 0 for 8 μs; otherwise set to 1 for 128 μs. B1-B6indicates the sealed value of the TXOP_DURATION B7 Coding 1 Indicateswhether BCC or LDPC is used: Set to 0 to indicate BCC Set to 1 toindicate LDPC

TABLE 11 Two Parts of Number HE-SIG-A Bit Field of bits Description B8LDPC Extra 1 Indicates the presence of the extra OFDM symbol Symbolsegment for LDPC: Segment Set to 1 if an extra OFDM symbol segment forLDPC is present Set to 0 if an extra OFDM symbol segment for LDPC is notpresent Reserved and set to 1 if the Coding field is set to 0 B9 STBC 1If the DCM field is set 0, then set to 1 if space time block coding isused. Neither DCM nor STBC shall be applied if both the DCM field adSTBC field are set to 1. Set to 0 otherwise. B10 Beam- 1 Set to 1 if abeamforming steering matrix is applied to formed the waveform in an SUtransmission. Set to 0 otherwise. B11-B12 Pre-FEC 2 Indcates the pre-FECpadding factor. Padding Set to 0 to indicate a pre-FEC padding factor of4 Factor Set to 1 to indicate a pre-FEC padding factor of 1 Set to 2 toindicate a pre-FEC padding factor of 2 Set to 3 to indicate a pre-FECpadding factor of 3 B13 PE 1 Indicates PE disambiguity as defined inDisambiguity 28.3.12 (Packet extension). B14 Reserved 1 Reserved and setto 1 B15 Doppler 1 Set to 1 if one of the following applies: The numberof OFDM symbols in the Data field is larger than the signaled midambleperiodicity plus 1 and the midamble is present The number of OFDMsymbols in the Data field is less than or equal to the signaled midambleperiodicity plus 1 (see 28.3.11.16 Midamble), the midamble is notpresent, but the channel is fast varying. It recommends that midamblemay be used for to PPDUs of the reverse link. Set to 0 otherwise.B16-B19 CRC 4 CRC for bits 0-41 of the HE-SIG-A field (see 28.3.10.7.3(CRC computation)). Bits 0-41 of the HE-SIG-A field correspond to bits0-25 of HE-SIG-A1 followed by bits 0-15 of HE-SIG-A2). B20-B25 Tail 6Used to terminate to trellis of the convolutional decoder. Set to 0.

In addition, the HE-SIG-A field of the HE MU PPDU may be defined asfollows.

TABLE 12 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionHE-STG-A1 B0 UL/DL 1 Indicates whether the PPDU is sent UL or DL. Set tothe value indicated by the TXVECTOR parameter UPLINK_FLAG. NOTE-The TDLSpeer can identify the TDLS frame by To DS and From DS fields is the MACheader of the MPDU. B1-B3 SIGB MCS 3 Indicates the MCS of the HE-SIG-Bfield: Set to 0 for MCS 0 Set to 1 for MCS 3 Set to 2 for MCS 3 Set to 3for MCS 3 Set to 4 for MCS 4 Set to 5 for MCS 5 The values 6 and 7 arereserved B4 SIGB DCM 1 Set to 1 indicates that the HE-SIG-B is modulatedwith DCM for the MCS. Set to 0 indicates that the HE-SIG-B is notmodulated with DCM for the MCS. NOTE-DCM is only applicable to MCS 0,MCS 1, MCS 3, and MCS 4 B5-B10 BSS Color 6 The BSS Color field is anidentifier of the BBS. Set to the value of the TXVECTOR parameterBSS_-COLOR. B11-B14 Spatial Reuse 4 Indicates whether or not spatialreuse is allowed during the transmission of this PPDU Set to the valueof the SPATIAL_REUSE parameter of the TXVECTOR, which contains a valuefrom Table 28-21 (Spatial Reuse field encoding for an HE SU PPDU, HE ERSV PPDU, and HE MU PPDU) (see 27.11.6 (SPATIAL_REUSE)). Set toSRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU. Setto SRP_AND_NON_ SRG_OBSS_PD_PROHIBITED to prohibit both SRP- basedspatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU.For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and27.9 (Spatial reuse operation).

TABLE 13 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB15-B17 Bandwidth 3 Set to 0 for 20 MHz. Set to 1 for 40 MHz. Set to 2for 80 MHz non-preamble puncturing mode. Set to 3 for 160 MHz and 80 +80 MHz non-preamble puncturing mode. If the SIGB Compression field is 0:Set to 4 for preamble puncturing in 80 MHz, where in the preamble onlythe secondary 20 MHz is punctured. Set to 5 for preamble puncturing in80 MHz, where in the preamble only one of the two 20 MHz sub- channelsin secondary 40 MHz is punctured. Set to 6 for preamble puncturing in160 MHz or 80 + 80 MHz, where in the primary 80 MHz of the preamble onlythe secondary 20 MHz is punctured. Set to 7 for preamble puncturing in160 MHz or 80 + 80 MHz, where in the primary 80 MHz of the preamble theprimary 40 MHz is present. If the SIGB Compression field is 1 thenvalues 4-7 are reserved. B18-B21 Number Of 4 If the HE-SIG-B Compressionfield is set to 0, indicates HE-SIG-B the number of OFDM symbols in theHE-SIG-B Symbols Or field: MU-MIMO Set to the number of OFDM symbols inthe HE-SIG-B Users field minus 1 if the number of OFDM symbols in theHE-SIG-B field is less than 16: Set to 15 to indicate that the number ofOFDM symbols in the HE-SIG-B field is equal to 16 if Longer Than 16 HESIG-B OFDM Symbols Support sub- field of the HE Capabilities elementtransmitted by at least on recipient STA is 0; Set to 15 to indicatethat the number of OFDM symbols in the HE-SIG-B field is greater than orequal to 16 if the Longer Than 16 HE SIG-B OFDM Symbols Support subfieldof the HE Capabilities element transmitted by all the recipients STAsare 1 and if the HE-SIG-B data rate is less than MCS 4 without DCM. Theexact number of OFDM symbols in the HE-SIG-B field is calclulated basedon the number of User fields in the HE-SIG-B content channel which isindicated by HE-SIG-B common field in this case. If the HE-SIG-BCompression field is set to 1, indicates the number of MU-MIMO users andis set to the number of NU-MIMO users minus 1 B22 SIGB 1 Set to 0 if theCommon field in HE-SIG-B is present. Compression Set to 1 if the Commonfield it HE-SIG-B is not present.

TABLE 14 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB23-B24 GI + LTF 2 Indicates the GI duration and HE-LTF size: Size Setto 0 to indicate a 4x HE-LTF and 0.8 μs GI Set to 1 to indicate a 2xHE-LTF and 0.8 μs GI Set to 3 to indicate a 2x HE-LTF and 1.6 μs GI Setto 3 to indicate a 4x HE-LTF and 3.2 μs GI B25 Doppler 1 Set to 1 if oneof the following applies: The number of OFDM symbols in the Data fieldis larger than the signaled midamble periodicity plus 1 and the midambleis present The number of OFDM symbols in the Data field is less than orequal to the signaled midamble periodicity plus 1 (see 28.3.11.16Midamble), the midamble is not present, but the channel is fast varying.It recommends that midamble may be use for the PPDUs of the reverselink. Set to 0 otherwise. HE-SIG-A2 B0-B6 TXOP 7 Set to 127 to indicateno duration information if TXVECTOR parameter TXOP_DURATION is set toUNSPECIFIED. Set to a value less than 127 to indicate durationinformation for NAV setting and protection of the TXOP as follows: IfTXVECTOR parameter TXOP_DURATION is less than 512, then B0 is set to 0and B1-B6 is set to floor(TXOP_DURATION/8) Otherwise, B0 is set to 1 andB1-B6 is set to floor ((TXOP_DURATION-512/128) where B0 indicates theTXOP length granularity. Set to 0 for 8 μs; otherwise set to 1 for 128μs. B1-B6 indicates the scaled value of the TXOP_DURATION B7 Reserved 1Reserved and set to 1

TABLE 15 TwoParts of Number HE-SIG-A Bit Field of bits DescriptionB8-B10 Number of 3 If the Doppler field is set to 0, indicates theHE-LTF number of HE-LTF symbols: Symbols And Set to 0 for 1 HE-LTFsymbol Midamble Set to 1 for 2 HE-LTF symbols Periodicity Set to 2 for 4HE-LTF symbols Set to 3 for 6 HE-LTF symbols Set to 4 for 8 HE-LTFsymbols Other values are reserved. If the Doppler field is set to 1B8-B9 indicates the number of HE-LTF symbols and B10 indicates midambleperiodicity. B8-B9 is encoded as follows: 0 indicates 1 HE-LTF symbol 1indicates 2 HE-LTF symbols 2 indicates 4 HE-LTF symbols 3 is reservedB10 is set to 0 if the TXVECTOR prameter MIDAMBLE_PERIODICITY is 10 andset to 1 if the TXVECTOR parameter PREAMBLE_ PERIODICITY is 20. B11 LDPCExtra 1 Indication of the presence of the extra OFDM symbol Symbolsegment for LDPC. Segment Set to 1 if an extra OFDM symbol segment forLDPC is present. Set to 0 otherwise. B12 STBC 1 In an HE MU PPDU whereeach RU includes no more than 1 user, set to 1 to indicate all RUs areSTBC encoded in the payload, set to 0 to indicate all RUs are not STBCencoded in the payload. STBC does not apply to HE-SIG-B. STBC is notapplied if one or more RUs are used for MU-MIMO allocation. B13-B14Pre-FEC 2 Indicates the pre-FEC padding factor. Padding Set to 0 toindicate a pre-FEC padding factor of 4 Factor Set to 1 to indicate apre-FEC padding factor of 1 Set to 2 to indicate a pre-FEC paddingfactor of 2 Set to 3 to indicate a pre-FEC padding factor of 3 B15 PE 1Indicates PE disambiguity as defined in Disambiguity 28.3.12 (Packetextersion) B16-B19 CRC 4 CRC for bits 0-41 of the HE-SIG-A field (see28.3.10.7.3 (CRC compuation)). Bits 0-41 of the HE-SIG-A fieldcorrespond to bits 0-25 of HE-SIG-A1 followed by bits 0-15 ofHE-SIG-A2). B20-B25 Tail 6 Used to terminate the trellis of theconvolutional decoder. Set to 0.

In addition, the HE-SIG-A field of the HE TB PPDU may be defined asfollows.

TABLE 16 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionHE-SIG-A1 B0 Format 1 Differentiate an HE SU PPDU and HE ER SU PPDU froman HE TB PPDU: Set to 0 for an HE TB PPDU B1-B6 BSS Color 6 The BSSColor field is an identifier of the BSS. Set to the value of theTXVECTOR parameter BSS_-COLOR. B7-B10 Spatial 4 Indicates whether or notspatial reuse is allowed in a Reuse 1 subband of the PPDU during thetransmission of this PPDU, and if allowed, indicates a value that isused to determine a limit on the transmit power of a spatial reusetransmission. If the Bandwidth field indicates 20 MHz, 40 MHZ, or 80 MHZthen this Spatial Reuse field applies to the first 20 MHz subband. Ifthe Bandwidth field indicates 160/80 + 80 MHz then this Spatial Reusefield applies to the first 40 MHz subband of the 160 MHz operating band.Set to the value of the SPATIAL_REUSE(1) parameter of the TXVECTOR,which contains a value from Table 28-22 (Spatial Reuse field encodingfor an HE TB PPDU) for an HE TB PPDU (see 27.11.6 (SPATIAL_REUSE)) Setto SRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU.Set to SRP_AND_NON_ SRG_OBSS_PD_PROHIBITED to prohibit both SRP- basedspatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU.For the interpretation of other values see 27.11.6 (SPATIAL _REUSE) and27.9 (Spatial reuse operation).

TABLE 17 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB11-B14 Spatial 4 Indicates whether or not spatial reuse is allowed in aReuse 2 subband of the PPDU during the transmission of this PPDU, and ifallowed, indicates a value that is used to determine a limit on thetransmit power of a spatial resuse transmission. If the Bandwidth fieldindicates 20 MHz, 40 MHz, or 80 MHz: This Spatial Reuse field applies tothe second 20 MHz subband. If the STA operating channel with is 20 MHz.then this field is set to the same value as Spatial Reuse 1 field. Ifthe STA operating channel width is 40 MHz. in the 2.4 GHz band, thisfield is set to the same value as Spatial Reuse 1 field. If theBandwidth field indicates 160/80 + 80 MHz the this Spatial Reuse fieldapplies to the second 40 MHz subband of the 160 MHz operating band. Setto the value of the SPATIAL_REUSE(2) parameter of the TXVECTOR, whichcontains a value from Table 28-22 (Spatial Reuse field encoding for anHE TB PPDU) for an HE TB PPDU (see 27.11.6 (SPATAL_REUSE)) Set toSRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU. Setto SRP_AND_NON_ SRG_OBSS_PD_PROHIBITED to prohibit both SRP- basedspatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU.For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and27.9 (Spatial reuse operation).

TABLE 18 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB15-B18 Spatial 4 Indicates whether or not spatial reuse is allowed in aReuse 3 subband of the PPDU during the transmission of this PPDU, and ifallowed, indicates a value that is used to determine a limit on thetransmit power of a spatial reuse transmsission. If the Bandwidth fieldindicates 20 MHz, 40 MHz, or 80 MHz: This Spatial Reuse field applies tothe third 20 MHz subband. If the STA operating channel width is 20 MHzor 40 MHz, is field is set to the same value as Spatial Reuse 1 field.If the Bandwidth field indicates 160/80 + 80 MHz: This Spatial Reusefield applies to the third 40 MHz subband of the 160 MHz operating band.If the STA operating channel width is 80 + 80 MHz this field is set tothe same value as Spatial Reuse 1 field. Set to the value of theSPATIAL_REUSE(3) parameter of the TXVECTOR, which contains a value fromTable 28-22 (Spatial Reuse field encoding for an HE TB PPDU) for an HETB PPDU (see 27.11.6 (SPATIAL_REUSE)). Set to SRP_DISALLOW to prohibitSRP-based spatial reuse during this PPDU. Set to SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP- based spatial reuse andnon-SRG OBSS PD-based spatial reuse during this PPDU. For theinterpretation of other values see 27.11.6 (SPATIAL_REUSE) and 27.9(Spatial reuse operation).

TABLE 19 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB19-B22 Spatial 4 Indicates whether or not spatial reuse is allowed in aReuse 4 subband of the PPDU during the transmission of this PPDU, and ifallowed, indicates a value that is used to determine a limit on thetransmit power of a spatial resuse transmission. If the Bandwidth fieldindicates 20 MHZ, 40 MHz or 80 MHz: This Spatial Reuse field applies tothe fourth 20 MHz subband. If the STA operating channel width is 20 MHz,then this field is set to the same value as Spatial Reuse 1 field. Ifthe STA operating channel width is 40 MHz, then this field is set to thesame value as Spatial Reuse 2 field. If the Bandwidth field indicates160/80 + 80 MHz. This Spatial Reuse field applies to the fourth 40 MHzsubband of the 160 MHz operating band. If the STA operating channelwidth is 80 + 80 MHz, then this field is set to same value as SpatialReuse 2 field. Set to the value of the SPATIAL_REUSE(4) parameter of theTXVECTOR, which contains a value from Table 28-22 (Spatial Reuse fieldencoding for an HE TB PPDU) for an HE TB PPDu (see 27.11.6(SPATIAL_REUSE)). Set to SRP_DISALLOW to prohibit SRP-based spatialreuse during this PPDU. Set to SRP_AND_NON_ SRB_OBSS_PD_PROHIBITED toprohibit both SRP- based spatial reuse and non-SRG OBSS PD-based spatialreuse during this PPDU. For the interpretation of other values see27.11.6 (SPATIAL_REUSE) and 27.0 (Spatial reuse operation). B23 Reserved1 Reserved and set to 1. NOTE-Unlike other Reserved fields in HE-SIG-Aof the HE TB PPDU, B23 does not have a corresponding bit in the Triggerframe. B24-B25 Bandwidth 2 Set to 0 for 20 MHz Set to 1 for 40 MHz Setto 2 for 80 MHz Set to 3 for 160 MHz and 80 + 80 MHz

TABLE 20 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionHE-SIG-A2 B0-B6 TXOP 7 Set to 127 to indicate no duration information ifTXVECTOR parameter TXOP_DURATION is set to UNSPECIFIED. Set to a valueless than 127 to indicate duration information for NAX setting andprotection of the TXOP as follows: if TXVECTOR parameter TXOP_DURATIONis less than 512, then B0 is set to 0 and B1-B6 is set tofloor(TXOP_DURATION/8) Otherwise, B0 is set to 1 and B1-B6 is set tofloor ((TXOP DURATION-512)/128) where B0 indicates the TXOP lengthgranularity. Set to 0 for 8 μs; otherwise set to 1 for 128 μs. B1-B6indicates the scaled value of the TXOP_DURATON B7-B15 Reserved 9Reserved and set to value indicated in the UL HE-SIG- A2 Reservedsubfield in the Trigger frame. B16-B19 CRC 4 CRC of bits 0-41 of theHE-SIG-A field. See 28.3.10.7.3 (CRC computation). Bits 0-41 of theHE-SIG-A field correspond to bits 0-25 of HE-SIG-A1 followed by bits0-15 of HE-SIG-A2) B20-B25 Tail 6 Used to terminate the trellis of theconvolutional decoder. Set to 0.

The HE-SIG-B 2040 may be included only for a multiple-user (MU) PPDU asdescribed above. Basically, the HE-SIG-A 2050 or the HE-SIG-B 2060 mayinclude resource allocation information (or virtual resource allocationinformation) for at least one receiving STA.

Hereinafter, technical features of channel bonding supported by the STAof the present disclosure will be described.

For example, in an IEEE 802.11n system, 40 MHz channel bonding may beperformed by combining two 20 MHz channels. In addition, 40/80/160 MHzchannel bonding may be performed in the IEEE 802.11ac system.

For example, the STA may perform channel bonding for a primary 20 MHzchannel (P20 channel) and a secondary 20 MHz channel (S20 channel). Abackoff count/counter may be used in the channel bonding process. Thebackoff count value may be chosen as a random value and decrementedduring the backoff interval. In general, when the backoff count valuebecomes 0, the STA may attempt to access the channel.

During the backoff interval, when the P20 channel is determined to be inthe idle state and the backoff count value for the P20 channel becomes0, the STA, performing channel bonding, determines whether an S20channel has maintained an idle state for a certain period of time (forexample, point coordination function interframe space (PIFS)). If theS20 channel is in an idle state, the STA may perform bonding on the P20channel and the S20 channel. That is, the STA may transmit a signal(PPDU) through a 40 MHz channel (that is, a 40 MHz bonding channel)including a P20 channel and the S20 channel.

FIG. 21 shows an example of channel bonding. As shown in FIG. 21 , aprimary 20 MHz channel and a secondary 20 MHz channel may configure aprimary 40 MHz channel through channel bonding. That is, a bonded 40 MHzchannel may include a primary 20 MHz channel and a secondary 20 MHzchannel.

Channel bonding may be performed when a channel that is contiguous to aprimary channel is in an idle state. That is, a primary 20 MHz channel,a secondary 20 MHz channel, a secondary 40 MHz channel, and a secondary80 MHz channel may be sequentially bonded. However, when the secondary20 MHz channel is determined to be in a busy state, even if the othersecondary channels are all in an idle state, the channel bonding may notbe performed. Additionally, when the secondary 20 MHz channel isdetermined to be in an idle state and the Secondary 40 MHz channel isdetermined to be in a busy state, channel bonding may be performed onlyon the primary 20 MHz channel and the secondary 20 MHz channel.

Hereinafter, preamble puncturing that is supported by a station (STA) ofthe present specification will be described.

For example, in the example of FIG. 21 , when a primary 20 MHz channel,a secondary 40 MHz channel, and a secondary 80 MHz channel are all in anidle state, while the secondary 20 MHz channel is in a busy state,bonding between the secondary 40 MHz channel and the secondary 80 MHzchannel may be impossible. In this case, the STA may configure a 160 MHzPPDU and puncture preambles (or perform preamble puncturing onpreambles) (e.g., L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, HE-SIG-A,HE-SIG-B, HE-STF, HE-LTF, EHT-SIG, EHT-STF, EHT-LTF, and so on) that aretransmitted through the secondary 20 MHz channel, thereby being capableof transmitting a signal through a channel that is in an idle state. Inother words, the STA may perform preamble puncturing on part of the bandof the PPDU. Information on the preamble puncturing (e.g., informationon the 20/40/80 MHz channel(s)/band(s) having puncturing appliedthereto) may be included in a signal field (e.g., HE-SIG-A, U-SIG,EHT-SIG) of the PPDU.

Hereinafter, technical features of a multi-link (ML) supported by an STAof the present disclosure will be described.

The STA (AP and/or non-AP STA) of the present disclosure may supportmulti-link (ML) communication. ML communication may refer tocommunication supporting a plurality of links. The link related to MLcommunication may include channels of the 2.4 GHz band shown in FIG. 15, the 5 GHz band shown in FIG. 16 , and the 6 GHz band shown in FIG. 17(for example, 20/40/80/160/240/320 MHz channels).

A plurality of links used for ML communication may be set in variousways. For example, a plurality of links supported by one STA for MLcommunication may be a plurality of channels in a 2.4 GHz band, aplurality of channels in a 5 GHz band, and a plurality of channels in a6 GHz band. Alternatively, a plurality of links supported by one STA forML communication may be a combination of at least one channel in the 2.4GHz band (or 5 GHz/6 GHz band) and at least one channel in the 5 GHzband (or 2.4 GHz/6 GHz band). Meanwhile, at least one of the pluralityof links supported by one STA for ML communication may be a channel towhich preamble puncturing is applied.

The STA may perform an ML setup to perform ML communication. The MLsetup may be performed based on a management frame or control frame suchas a Beacon, a Probe Request/Response, an Association Request/Response,and the like. For example, information about ML setup may be included inan element field included in a Beacon, a Probe Request/Response, anAssociation Request/Response, and the like.

When ML setup is completed, an enabled link for ML communication may bedetermined. The STA may perform frame exchange through at least one of aplurality of links determined as an enabled link. For example, theenabled link may be used for at least one a management frame, a controlframe, and a data frame.

When one STA supports a plurality of links, a transceiver supportingeach link may operate as one logical STA. For example, one STAsupporting two links could be expressed as one multi-link device (MLD)including a first STA for a first link and a second STA for a secondlink. For example, one AP supporting two links could be expressed as oneAP MLD including a first AP for a first link and a second AP for asecond link. In addition, one non-AP supporting two links may beexpressed as one non-AP MLD including a first STA for the first link anda second STA for the second link.

Hereinafter, more specific features related to the ML setup aredescribed.

The MLD (the AP MLD and/or the non-AP MLD) may transmit informationabout a link that the corresponding MLD can support through ML setup.Link information may be configured in various ways. For example,information about the link may include at least one of 1) information onwhether the MLD (or STA) supports simultaneous RX/TX operation, 2)information on the number/upper limit of uplink/downlink links supportedby the MLD (or STA), 3) information about the location/band/resource ofthe uplink/downlink link supported by the MLD (or STA), 4) informationon available or preferred frame types (management, control, data, etc.)in at least one uplink/downlink link, 5) ACK policy informationavailable or preferred in at least one uplink/downlink link, and 6)information on available or preferred traffic identifier (TID) in atleast one uplink/downlink link. The TID is related to the priority oftraffic data and is expressed as eight types of values according to theconventional wireless LAN standard. That is, eight TID valuescorresponding to four access categories (AC) (AC_BK(background),AC_BE(best effort), AC_VI(video), AC_VO(voice)) according to theconventional WLAN standard may be defined.

For example, it may be pre-configured in advance that all TIDs aremapped for uplink/downlink link. Specifically, when negotiation is notmade through ML setup, all TIDs are used for ML communication. If themapping between the uplink/downlink link and the TID is negotiatedthrough additional ML settings, the negotiated TID may be used for MLcommunication.

A plurality of links usable by the transmitting MLD and the receivingMLD related to ML communication may be configured through ML setup, andthis may be referred to as an “enabled link”. The “enabled link” may becalled differently in various expressions. For example, it may bereferred to as various expressions such as a first link, a second link,a transmission link, and a reception link.

After the ML setup is completed, the MLD may update the ML setup. Forexample, the MLD may transmit information about a new link when it isnecessary to update information about the link. Information on the newlink may be transmitted based on at least one a management frame, acontrol frame, and a data frame.

According to an embodiment, the MLD may include a non-AP MLD and anAP-MLD. The non-AP MLD and the AP-MLD may be classified according to thefunction of an access point (AP). The non-AP MLD and the AP-MLD may bephysically separated or logically separated. For example, when the MLDperforms an AP function, it may be referred to as an AP MLD, and whenthe MLD performs an STA function, it may be referred to as a non-AP MLD.

Hereinafter, in the present specification, an MLD has one or more STAsconnected thereto and one MAC service access point (SAP) that isconnected to a logical link control (LLC). The MLD may mean a physicaldevice or mean a logical device. Hereinafter, the term device may meanan MLD.

Additionally, an MLD may include at least one STA being connected toeach link of a multi-link. For example, a processor of an MLD maycontrol the at least one STA. For example, the at least one STA may eachbe independently configured and may operate independently. The at leastone STA may each include a processor and a transceiver. For example, theat least one STA may operate independently regardless of the processorof the MLD.

Hereinafter, for simplicity in the description, it will be described inthe present disclosure that an MLD (or a processor of an MLD) controlsat least one STA. However, the present disclosure will not be limited tothis. As described above, the at least one STA may independentlytransmit and/or receive signals regardless of the MLD.

According to an embodiment, an AP MLD or a non-AP MLD may be configuredto have a structure having multiple links. In other words, a non-AP MLDmay support multiple links. A non-AP MLD may include a plurality ofSTAs. The plurality of STAs may have a link per STA.

The EHT specification (802.11be specification) considers a multi-linkdevice (MLD) structure, wherein one AP/non-AP MLD supports multiplelinks, as a main technology. An STA that is included in a non-AP MLD maydeliver (or transfer) information on other STAs within the non-AP MLDtogether through one link. Accordingly, this has an effect of reducingoverhead of a frame exchange. Additionally, this also has the effect ofincreasing link usage efficiency and reducing power consumption of theSTA.

FIG. 22 shows an exemplary structure of a non-AP MLD.

Referring to FIG. 22 , a non-AP MLD may be configured to have astructure having multiple links. In other words, a non-AP MLD maysupport multiple links. A non-AP MLD may include a plurality of STAs.The plurality of STAs may have a link per STA. Although FIG. 22 shows anexemplary structure of a non-AP MLD, the structure of an AP MLD may alsobe configured identically as the non-AP MLD structure shown in FIG. 22 .

For example, a non-AP MLD may include STA 1, STA 2, and STA 3. STA 1 mayoperate on Link 1. Link 1 may be included within a 5 GHz band. STA 2 mayoperate on Link 2. Link 2 may be included within a 6 GHz band. STA 3 mayoperate on Link 3. Link 3 may be included within a 5 GHz band. The bandsin which Link 1/2/3 are included are merely exemplary, and, therefore,the links may also be included within 2.4, 5, and 6 GHz.

As described above, in case of the AP/non-AP MLD supporting multi-link,each AP of the AP MLD and each STA of the non-AP MLD may be connected toeach link through a link setup process. And, the link that is connectedat this point may be switched or reconnected to another link, by the APMLD or non-AP MLD, depending upon the circumstances.

Additionally, in the EHT specification, in order to reduce powerconsumption, the link may be divided into an anchored link and anon-anchored link. An anchored link or a non-anchored link may bereferred to as various terms. For example, an anchored link may bereferred to as a primary link. And, a non-anchored link may be referredto as a secondary link.

According to an embodiment, an AP MLD supporting multi-link may managethe links by designating each link as an anchored link or a non-anchoredlink. The AP MLD may support one or more links, among the plurality oflinks, as anchored links. The non-AP MLD may use anchored links byselecting one or more of its anchored links from an anchored link list(i.e., a list of anchored links that are supported by the AP MLD).

For example, an anchored link may not only be used in a frame exchangefor synchronization but may also be used for a non-data frame exchange(i.e., beacon and management frame). Additionally, a non-Anchored linkmay be used only for a data frame exchange.

During an idle period, the non-AP MLD may perform monitoring on (ormonitor) only the anchored links in order to receive a beacon andmanagement frame. Therefore, in case of the non-AP MLD, the non-AP MLDshould be connected to at least one anchored link in order to receive abeacon and management frame. The one or more anchored links shouldalways maintain an enable state. Conversely, a non-anchored link is usedonly for data frame exchange. Therefore, an STA corresponding to anon-anchored link (or an STA that is connected to a non-anchored link)may enter a doze mode during an idle period that does not used achannel/link. By doing so, this has an effect of reducing powerconsumption.

Hereinafter, a protocol enabling the AP MLD or non-AP MLD to dynamicallyrecommend or request link reconnection for an efficient link connection,depending upon the circumstances, may be proposed. Additionally,hereinafter, in the present specification, an anchored link reconnectionprotocol, which is based on an anchored link that is not only used as ageneral link but also used for the purpose of power reduction, may beadditionally proposed.

Embodiment for Link Switching and Reconnection

According to an embodiment, each link between an AP MLD and a non-AP MLDmay be determined during an association or (re)association process. TheAP MLD and the non-AP MLD may perform frame exchange through a link thatis connected at this point. A detailed embodiment of an AP MLD and anon-AP MLD being connected through a link setup process may be describedwith reference to FIG. 23 .

FIG. 23 shows an exemplary connection between an AP MLD and a non-AP MLDthrough a Link setup process.

Referring to FIG. 23 , an AP MLD may include AP 1, AP 2, and AP 3. And,a non-AP MLD may include STA 1 and STA 2. AP 1 and STA 1 may beconnected through Link 1. And, AP 2 and STA 2 may be connected throughLink 2.

For example, AP 1 and STA 1 may be connected by Link 1 through a firstlink setup process. AP 2 and STA 2 may be may be connected by Link 2through a second link setup process. As another example, an AP MLD and anon-AP MLD may be connected through a single link setup process. Inother words, an AP MLD and a non-AP MLD may be connected through Link 1and Link 2 based on a single link setup process.

As described above, each AP and STA may perform frame exchange throughits connected link. Additionally, information on other link(s) relatedto other APs or information on other link(s) related to other STAs maybe transmitted and/or received through one link.

However, after performing the above-described link setup process, for amore efficient frame exchange (e.g., load balancing or interferenceavoiding, and so on) depending upon the circumstances/environment, theAP MLD or non-AP MLD may request a link switching or reconnection.

An embodiment related to link switching or reconnection may be describedwith reference to FIG. 24 .

FIG. 24 shows an example of a link being switched or reconnected.

Referring to FIG. 24 , in the existing structure, STA 2 is connected toAP 2. Thereafter, the data load of AP 2 may become excessive.Accordingly, STA 2 may be reconnected to AP 3, which has a comparativelysmaller data load. In this case, this has an effect of enabling the APMLD and the non-AP MLD to perform an efficient data exchange.

FIG. 25 shows a detailed example of a link being switched orreconnected.

Referring to FIG. 25 , AP 1 of the AP MLD may be connected to STA 1 ofthe non-AP MLD through Link 1. AP 2 of the AP MLD may be connected toSTA 2 of the non-AP MLD through Link 2. Thereafter, STA 2 mayattempt/request a connection to AP 3 through a link switching orreconnection, and STA 2 may be connected to AP 3 through Link 2, basedon the link switching or reconnection.

According to an embodiment, the AP MLD and the non-AP MLD may transceive(or transmit and/or receive)/exchange various information per currentlink and information related to a link state. Therefore, the AP MLD andthe non-AP MLD may select a link that is more appropriate (or adequate)for transmitting and/or receiving signals, based on the variousinformation per current link and information related to the link state.For example, the various information per current link may includeinformation on data traffic load per link and information on channelaccess capability between links. For example, the link state may beconfigured as disable or enable, and so on.

Hereinafter, in the present specification, a process during which an APMLD/non-AP MLD negotiates with a non-AP MLD/AP MLD in order to requestswitching or reconnecting to a link other than the initially connectedlink, so as to increase its performance, may be referred to as “linkswitching negotiation”. The term “Link switching negotiation” may alsobe referred to as many other terms, and, therefore, the term may also bechanged.

Hereinafter, the link switching or reconnection process may be describedby being divided into a case where the process is requested by an AP MLDand a case where the process is requested by a non-AP MLD.

Embodiment of an AP MLD Requesting Link Switching or Reconnection

According to an embodiment, an AP MLD may request a link switching orreconnection, to a non-AP MLD, for an efficient data transmission. Forexample, for load balancing, the AP MLD may request, to an STA, toswitch or reconnect its link to a more efficient link based on datatraffic of each AP.

For example, the AP MLD may calculate/verify/confirm (or finalize) alink that is appropriate for the STAs of the non-AP MLD, based on datatraffic load information per AP and/or channel access capabilityinformation between each link (e.g., information related to SimultaneousTX/RX (STR) capability, and so on). Thereafter, the AP MLD may request,to the STA (or non-AP MLD), a link switching or reconnection, based onthe data traffic load information per AP and/or channel accesscapability information between each link.

As described above, when requesting a link switching, the AP MLD maytransmit information on a link that is considered to be the mostappropriate link, to the AP MLD, through a request message. For example,the request message may include a beacon or management frame, and so on.

Regarding the above-described embodiment, an element or field includinglink information on the link that is considered to be most appropriatemay be newly proposed. The newly proposed element or field may bedefined as a “recommended link”. The term “recommended link” is merelyexemplary, and, therefore, the detailed term of the element or field maybe changed.

recommend link (element/field): This is an element or field that enablesthe AP MLD to recommend a link that is most appropriate to an STA of thenon-AP MLD, based on various information per link (e.g., data load perlink, and so on). For example, the recommend link (element/field) may beindicated as link ID information of the AP MLD or AP BSS information,and so on. In other words, the recommend link (element/field) mayinclude link ID information of the AP MLD or AP BSS information, and soon.

According to an embodiment, the recommend link (element/field) may beoptionally included in a link switching response and may then betransmitted. For example, an STA may establish connection to the linkthat is recommended by the AP, based on the corresponding element/field(i.e., recommend link). As another example, an STA may also perform aconnection request to a link other than the indicated link, based on thecorresponding element/field (i.e., recommend Link) and additionalinformation that the STA has (or possesses).

A detailed signal exchange process of the AP MLD and non-AP MLDaccording to the above-described embodiment may be described withreference to FIG. 26 .

FIG. 26 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

Referring to FIG. 26 , in a situation where STA 2 is connected to AP 2through Link 2, a large amount of data traffic may be concentrated to AP2. In other words, in a situation where STA 2 is connected to AP 2through Link 2, a large data traffic may occur in AP 2.

The AP MLD (or AP 2) may request, to the non-AP MLD (or STA 2), areconnection to AP 3, which has a relatively smaller number of STAconnections. Generally, a message for requesting reconnection istransmitted to an STA (i.e., STA 2) that wants to be reconnected.However, depending upon the situation (e.g., a channel situation or linkstate), the message may also be transmitted to any STA (i.e., otherSTA). In other words, an STA to which the request message for requestingreconnection (e.g., link switching request frame) is transmitted may bechanged.

For example, when an STA that has received the request message forrequesting the reconnection (i.e., STA 2) accepts the request, the STAmay transmit a response message of “Accept” (e.g., link switchingresponse frame). As another example, if the STA (i.e., STA 2) rejects(or declines) the request, the STA may transmit a response message of“Decline”.

In case of the response message, the STA (i.e., STA 2) that accepts thereconnection generally transmits the response message to the initiallink (the connection link before the reconnection). However, by usingthe characteristics of a multi-link, the response message may also betransmitted through any other link (i.e., other STA).

If STA 2 accepts the link reconnection request, after transmitting theresponse message, STA 2 may disconnect its initial connection to AP 2and may request a link reconnection with AP 3. At this point, thereconnection request process may be performed identically as theexisting link setup process between the MLDs. After completing the linksetup process between AP 3 and STA 2, STA 2 may perform a frame exchangewith AP 3 through Link 2.

Conversely, if STA 2 declines the link reconnection request, STA 2 andAP 2 may continue to use their initially connected link (i.e., Link 2)as it is.

According to an embodiment, when the AP request for a link switching tothe STA, and when an adequate link is recommended, the STA may switch ormay not switch the link to the recommended link. For example, in orderto enable the AP to recommend an appropriate link to the STA, theabove-described recommend link may be used.

For example, as a response message to the request message for requestinga reconnection of the AP, the STA may accept the link switching. The STAmay accept/verify the link switching to the recommended link, and theSTA may also request other link switching to the AP, based on otherinformation apart from the information included in the request message.

Therefore, the AP needs to notify the STA of the acceptance ornon-acceptance (or declination) of the response message. For this, theAP may transmit, to the STA, a confirmation message (e.g., linkswitching confirmation frame) corresponding to the response message(e.g., link switching response frame) of the STA.

Detailed operations of the AP MLD and the non-AP MLD according to theabove-described embodiment may be described with reference to FIG. 27 .

FIG. 27 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

Referring to FIG. 27 , AP 2 may request for a link switching to STA 2including recommended link information. In other words, AP 2 maytransmit, to STA 2, a link switching request frame including recommendedlink information.

STA 2 may transmit acceptance or declination of the link request througha link switching response frame.

For example, when the link switching is accepted, STA 2 may includeinformation on the link that is to be switched to the link switchingresponse frame and may then transmit the link switching response frame.At this point, the information on the link that is to be switched may bethe same or may not be the same as the recommended link.

As another example, when STA 2 selects another link other than therecommended link that is provided by AP 2 and responds to the requestthrough the link switching response frame, the AP may transmit a messagecorresponding to a final acceptance or non-acceptance to the response tothe STA. The corresponding message may be referred to as a linkswitching confirmation frame.

For example, AP 2 may accept the link switching to the link designatedby STA 2, through the link switching confirmation frame. STA 2 mayattempt to perform the link switching to its designated link, based onthe link switching confirmation frame.

As another example, AP 2 may decline the link switching to the linkdesigned by STA 2, through the link switching confirmation frame. STA 2and AP 2 may maintain their connections to their initial link withoutany link switching.

The embodiment shown in FIG. 27 may also be applied to a case where theAP has transmitted a link switching request frame without including therecommended link information. For example, when the AP (e.g., AP 2) hastransmitted the link switching request frame to the STA (e.g., STA 2)without including any recommended link information, after directlydesignating the link that is to be switched, based on the informationbelonging to (or possessed by) the STA, the STA may response to the APthrough the link switching response frame. In this case, also, the APshould transmit a link switching confirmation frame corresponding to afinal acceptance. Therefore, an embodiment of the AP transmitting a linkswitching confirmation frame, even in a case where the recommended linkinformation is not included in the link switching request frame, may beapplied.

Embodiment of a Non-AP MLD Requesting Link Switching or ReconnectionNon-AP MLD

According to an embodiment, a non-AP MLD may request link switching orreconnection to an AP MLD for efficient data transmission. For example,in order to use STR capability when performing data transmission, thenon-AP MLD may request, to the AP MLD, switching or reconnection of theconnected link.

FIG. 28 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

Referring to FIG. 28 , an AP MLD and a non-AP MLD may perform linkswitching negotiation. STA 2 of the non-AP MLD may transmit a linkswitching request frame to AP 2 of the AP MLD. As a response to the linkswitching request frame, AP 2 of the AP MLD may transmit a linkswitching response frame to STA 2 of the non-AP MLD. Although the linkswitching request frame or link switching response frame may betransmitted and/or received through a link, which is the target of theswitching, the present disclosure will not be limited only to this. Thelink switching request frame or link switching response frame may notonly be transmitted/received through also be a link, which is the targetof the switching, but may also be transmitted through other variouslinks.

A non-AP MLD may request link switching or reconnection through variousmethods. Hereinafter, 3 different methods for requesting link switchingor reconnection by the non-AP MLD may be proposed. More specifically,the 3 different methods may be described in the order of a solicitedmethod, an unsolicited method, and a general method.

1) Solicited method: This is a method for requesting various informationfor link (re)selection, by a non-AP MLD to an AP MLD, and requestinglink (re)selection, by the non-AP MLD, based on the receivedinformation. According to an embodiment, a method for requestinginformation of other APs of a connected AP MLD, by an STA, may not onlybe used for a case of reconfiguring a link but may also be used forvarious other cases. Therefore, the AP that has received an informationrequest message may transmit all of capability information, BSSparameter information, critical parameters, and/or operation elementinformation, and so on, for all APs within the AP MLD. Theabove-described example may all be applied to the embodiment that willbe described as follows.

2) Unsolicited method: This is a method for transmitting variousinformation for link (re)selection, by an AP, and requesting link(re)selection, by the AP, based on the received information, withouthaving a non-AP MLD make any separate information request. According toan embodiment, a method for requesting information of other APs of aconnected AP MLD, by an STA, may not only be used for a case ofreconfiguring a link but may also be used for various other cases.Therefore, the AP that has received an information request message maytransmit all of capability information, BSS parameter information,critical parameters, and/or operation element information, and so on,for all APs within the AP MLD. The above-described example may all beapplied to the embodiment that will be described as follows.

3) General method: This is a method of requesting a link (re)selection,by a non-AP MLD, without additional information based on variousinformation that are obtained through a previous beacon frame.

1) Solicited Method

Hereinafter, an embodiment related to the above-described solicitedmethod may first be described.

According to the embodiment, a non-AP MLD may request, to an AP MLD,information for selecting an appropriate link before the link switchingor reconnection. An STA may use data load information per AP orcapability information per link (or information of other links) forselecting the appropriate link.

For example, the capability information per link may be included in abeacon frame, and so on, and periodically transmitted.

As another information, as optional information, the capabilityinformation per link may not be included in a beacon frame, which istransmitted at each cycle period. Alternatively, in order to reduceframe overhead, an STA may receive only the information of a connectedlink or the information of an associated part of a link. Alternatively,when a beacon reception cycle period is long due to the characteristicsof a non-AP MLD (e.g., low-power device), the non-AP MLD may not becapable of receiving the capability information per link for selecting amore appropriate link.

In the above-described cases, the non-AP MLD may request recentinformation of the capability information per link and information perlink of the AP MLD. The links corresponding to the capabilityinformation per link and information per link may not only include thelink being transmitted and/or received but may also include otherlink(s). For example, a field of a QoS data frame (A-Control field ofthe 11ax specification), a management frame, a probe response frame, aPS-poll frame or a null frame may be used for requesting/transmittingrecent information. Alternatively, in order to request/transmit recentinformation, a separate new frame may be defined.

According to an embodiment, in order to request recent information ofthe capability information per link and information per link of the APMLD, the STA may transmit, to an AP, a request message requestinginformation needed for link reselection. For example, a probe requestframe that is defined in the related art may be reused for the requestmessage. As another example, a new frame for the request message mayalso be defined.

According to an embodiment, the STA may designate specific informationthat is needed and may request the designated information to the AP. Thespecific information that may be designated may be changed dependingupon the circumstances. That is, the STA may request only theinformation corresponding to a specific link or may request only theinformation corresponding to a specific capability. For example, theinformation corresponding to a specific link may include informationrelated to BSS load/parameters of a specific link. Additionally, theinformation corresponding to a capability may include BSS loadinformation of all links or BSS load information of a specific link. Inthis case, the AP may transmit only the information designated by theSTA through a response message. A detailed embodiment related to thespecific information request and response may be described through anembodiment related to the definition and operation of IOM.

As another example, the STA may request all capability information(e.g., including information of other link(s)) currently carried by theAP MLD through the request message.

As described in the above-described example, an embodiment fortransmitting all information carried by the AP or an embodiment fortransmitting only specific information designated by the STA may bevariously defined/configured. For example, the AP may transmit allinformation or designated information based on a separate field orbitmap, and so on.

Generally, although a message requesting information to the AP MLD maybe transmitted through an STA requesting reconnection, the message mayalso be transmitted to any STA (i.e., other STA(s)) depending upon thecircumstances (channel situation or link state).

The AP MLD that has received the request message may transmit, to thenon-AP MLD, a response message (i.e., information message) including therecent information (e.g., data load information per link, STR capabilityinformation between links, and so on) that is needed for linkreselection. For example, when a probe request frame of the prior artspecification is reused for the request message, the AP (or AP MLD)should respond to the request message by using a probe response frame asthe response message.

Although the response message may also be generally transmitted throughthe AP that has received the request message, the response message mayalso be transmitted to any AP (i.e., other AP(s)) by using thecharacteristics of a multi-link.

Optionally, the AP MLD may transmit a “recommend link” element, whichrecommends an appropriate link to the STA, together through a responsemessage including the above-described various information (e.g., recentinformation needed for link reselection).

Hereinafter, in order to be differentiated from a request message forlink switching and a response message for link switching, theabove-described request message and response message may be described asan information request message and an information response message.

The STA may reselect an appropriate link and request a link switching orreconnection, to the AP MLD, through a request message for linkswitching, based on the information included in the above-describedinformation response message. The request message for link switching mayinclude information on the AP that is to be reconnected to thecorresponding STA and link information.

When the AP MLD that has received the request message accepts therequest, the AP MLD may transmit a response message of “Accept”. And,when the AP MLD rejects (or declines) the request, the AP MLD maytransmit a response message of “Decline”.

When the request is accepted, the AP may perform link (re)setup based ona frame exchange through a link with a reselected AP starting from afterthe response message transmission. Conversely, when the request isdeclined, the STA may continue to use its initially connected link as itis.

An example of detailed AP MLD and non-AP MLD operations according to thesolicited method may be described with reference to FIG. 29 .

FIG. 29 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

Referring to FIG. 29 , when STA 2 of a non-AP MLD wants to reselect itsconnected link, STA 2 may transmit an info request message to the non-APMLD through Link 2. After receiving the info request message, the AP MLDmay transmit an info response message including information that isneeded for the link reselection of the non-AP MLD. STA 2 of the non-APMLD may transmit a request message for link switching (i.e., linkswitching request frame) to AP 2 of the AP MLD, based on the informationincluded in the above-described info response message. Thereafter, STA 2may receive a response message for link switching (i.e., link switchingrequest frame) and may perform link (re)set-up for link switching.

The embodiment related to information request that is proposed in thepresent specification may also be used/applied to a case where the STArequests necessary (or needed) information to the AP. When theinformation included in the frame (e.g., beacon) received by the STAfrom the AP is insufficient, the STA may request the insufficient (orlacking) information to the AP. For example, when the AP transmits onlythe information on a connected link without including information onother link(s), or when the AP transmits only information related toupdate or non-update on information of other link(s), the STA mayrequest the insufficient (or lacking) information to the AP.

A detailed example of the embodiment may be described with reference toFIG. 30 .

FIG. 30 shows an operation on a non-AP MLD for requesting information onother AP(s).

Referring to FIG. 30 , an AP MLD (or AP 1 to AP 3) may transmit onlyinformation related to the update or non-update on information of otherAP(s) (i.e., link(s)) to an STA through a beacon frame. Therefore, STA 2may transmit an info request message (or info request frame) to AP 2.STA 2 may receive an info response message (or info message) based onthe info request message. STA 2 may receive/obtain information relatedto other AP(s) based on the info response message.

For example, other AP information (e.g., BBS load, and so on) of the APMLD may not be included in the beacon, or AP 2 may transmit only theinformation related to the update or non-update (e.g., version/updateversion) on the other AP information.

STA 2 may need information of AP 1 (or information related to AP 1). STA2 may request the necessary information through AP 2. STA 2 may obtaininformation of AP 1 through a response message to the request. STA 2 mayuse the information of AP 1 for reselecting an appropriate link for linkswitching. For example, a frame for link switching may be variouslyconfigured.

Hereinafter, a new element/field including information for selecting anappropriate link, by an STA of the non-AP MLD, may be proposed.

For example, an “STA ratio per Link” (element/field) may be proposed.The “STA ratio per Link” may include information related to a number ofconnected STAs ratio per link. A detailed example of the “STA ratio perLink” may be described with reference to FIG. 31 .

FIG. 31 shows a detailed example of an STA ratio per Link.

Referring to FIG. 31 , the STA ratio per Link (element/field) mayinclude information related to a number of STAs or STA ratio beingconnected to each link in the entire AP MLD.

For example, when a total of 50 STAs are connected to an AP MLD having 3links, 10 STAs may be connected to Link 1, and 20 STAs may be connectedto Link 2. The AP MLD may transmit information on the connected STAs perlink as information related to a value or ratio (%), to the non-AP MLD,through the STA ratio per Link (element/field).

For example, when information on the connected STAs per link isexpressed as a value, Link 1 may be expressed/configured as 10, and Link2 may be expressed/configured as 20. Therefore, the value of STA ratioper Link 1 may be configured to be equal to 10. Additionally, the valueof STA ratio per Link 2 may be configured to be equal to 20.

As another example, when information on the connected STAs per link isexpressed as a ratio, Link 1 may be expressed/configured as 20 (10/50)%,and Link 2 may be expressed/configured as 40 (20/50)%. Therefore, thevalue of STA ratio per Link 1 may be configured to be equal to 20.Additionally, the value of STA ratio per Link 2 may be configured to beequal to 40.

The above-described example is merely exemplary, and the information onthe connected STAs per link may be variously configured. Apart from theabove-described example, the information on the connected STAs per linkmay be configured to be equal to a relative value.

The STA may verify/obtain a number and ratio of STAs being connected perlink, based on the above-described information on the connected STAs perlink, and this may be used as information for link selection.

According to an embodiment, apart from the above-described “STA ratioper Link” (element/field), various information/element(s)/field(s) maybe included in an information response message. For example, thefollowing information/element(s)/field(s) may be included in aninformation response message.

-   -   BSS load information per AP    -   STR capability information between links    -   TXOP information per link    -   NAV information per link    -   Recommended link information (i.e., “recommend Link” element)    -   Connected STA ratio information per link (i.e., “STA ratio per        Link” element)    -   other

Apart from the above-described information/element(s)/field(s), variousinformation needed for link selection may be included in the informationresponse message and may then be transmitted.

The STA that has received information, such as the information describedin the above-described example, selects an AP that the STA intends toswitch or reconnect, based on the received information, and, then, theSTA may transmit a request message for requesting reconnection of thelink. When the AP MLD that has received the request message accepts therequest, the AP MLD may transmit a response message of “Accept”. And,when the AP MLD rejects (or declines) the request, the AP MLD maytransmit a response message of “Decline”.

When the request is accepted, the AP may perform a frame exchangethrough a link with the reselected AP starting from after the responsemessage transmission. Conversely, when the request is declined, the STAmay continue to use its initially connected link as it is.

2) Unsolicited Method

Unlike the solicited method, wherein the non-AP MLD directly requestsadditional information, according to the unsolicited method, the AP MLDmay transmit additional information to the non-AP MLD through a beaconframe or a separate frame (e.g., field of a QoS data frame (A-Controlfield of the flax specification), management frame, FILS discoveryframe, unsolicited probe response frame, PS-Poll frame or null frame,and so on) without any additional information request from the non-APMLD. As another example, a new frame may be defined as a frame fortransmitting additional information to the non-AP MLD.

For example, when a beacon period is rather long, the mandatoryinformation needed for link switching by the non-AP MLD may beinsufficient or may not be the recent information. Therefore, the AP maytransmit a frame including link capability information of the AP MLD tothe non-AP MLD. Thereafter, the non-AP STA may obtain recent informationon the capability per link of the AP MLD. The frame may be periodicallytransmitted or may be aperiodically transmitted.

For example, when the frame is transmitted periodically, the AP maytransmit a frame for sharing the recent information of the AP. At thispoint, the time interval should be shorter than the cycle period of thebeacon that is transmitted by the AP. Additionally, when a FILSDiscovery frame is used as the frame, the frame may be transmitted foreach 20 us. As another example, a cycle period that is negotiatedthrough a capability negotiation between the AP and the STA may also beused. For example, a transmission period may be indicated through“periodic” field and “interval” field/subfield values of an IOMcapability element.

As another example, when the frame is transmitted aperiodically, the APmay transmit the frame each time an update event occurs in theinformation (capability, BSS parameter, operation element) of the AP. Asa detailed example, each time the link capability of the AP changes, thechanged information may be transmitted to the connected STA. In thiscase, the STA may maintain the recent information on the linkcapability.

According to the above-described example, since the non-AP STA does nottransmit a separate request message for obtaining a link capability,this may have an effect of a frame exchange overhead occurringrelatively less as compared to the solicited method. Additionally, sincethe STA may receive updated information each time main information isupdated, this may have an effect of enabling the STA to usefully use thereceived information.

An example of detailed AP MLD and non-AP MLD operations according to theunsolicited method may be described with reference to FIG. 32 .

FIG. 32 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

Referring to FIG. 32 , the AP MLD may transmit mandatory informationrequired for link reselection without any separate request message fromthe non-AP MLD to the non-AP MLD through a separate frame (e.g., infomessage).

According to an embodiment, unlike FIG. 32 , the AP MLD may transmit, toan STA, information on link capability through a field of a DL frame(e.g., QoS data frame), which the AP MLD transmits to the non-AP MLD,without any separate request message from the non-AP MLD. The operationsof the AP MLD and the non-AP MLD according to the embodiment may bedescribed with reference to FIG. 33 .

FIG. 33 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

Referring to FIG. 33 , AP 2 may transmit information of another AP (orinformation related to another AP) to STA 2, based on a DL frame (i.e.,DL 1). In other words, the DL frame may include information related toanother AP. For example, the information on the other AP may be includedin an A-Control field, and so on, of the 802.11ax specification.According to the embodiment, since an existing DL frame is used withoutany separate message, this has an effect of reducing frame overhead. Ifreal-time of the information is needed due to a change in criticalinformation of the other AP, update information may be transmittedthrough a separate message as shown in the embodiment of FIG. 32 .

For example, critical information of the AP may include A to Q, asfollows.

A. Inclusion of a Channel Switch Announcement element

B. Inclusion of an Extended Channel Switch Announcement element

C. Modification of the EDCA parameters element

D. Inclusion of a Quiet element

E. Modification of the DSSS Parameter Set

F. Modification of the CF Parameter Set element

G. Modification of the HT Operation element

H. Inclusion of a Wide Bandwidth Channel Switch element

I. Inclusion of a Channel Switch Wrapper element

J. Inclusion of an Operating Mode Notification element

K. Inclusion of a Quiet Channel element

L. Modification of the VHT Operation element

M. Modification of the HE Operation element

N. Insertion of a Broadcast TWT element

O. Inclusion of the BSS Color Change Announcement element

P. Modification of the MU EDCA Parameter Set element

Q. Modification of the Spatial Reuse Parameter Set element

Therefore, the non-AP MLD may obtain recent link capability informationregardless of the cycle period (or periodicity) of the beacon frame. Thenon-AP MLD may select an appropriate link when performing linkswitching, based on information that is received. The STA may reselectan appropriate link and may request the AP MLD for link switching orreselection, based on the received information. The request informationmay include information on the AP and information on the link to whichthe STA is to be reconnected. Additionally, when the AP MLD that hasreceived the request message accepts the request, the AP MLD maytransmit a response message of “Accept”. And, when the AP MLD rejects(or declines) the request, the AP MLD may transmit a response message of“Decline”.

When the request is accepted, the AP may perform link (re)setup througha frame exchange with a link of a reselected AP starting from after theresponse message transmission. Conversely, when the request is declined,the STA may continue to use its initially connected link as it is.

3) General Method

According to a general method, the non-AP MLD may request link switchingor reconnection without any additional information request based on theinformation the non-AP MLD currently carries (or possesses). Theinformation that is used at this point may include information on the APMLD and information on the non-AP MLD (e.g., information on STRcapability per link, information on link state (enable/disable), and soon) that are included in a previously received beacon or managementframe, and so on.

Unlike the unsolicited method, the STA may transmit, to the APMLD, arequest message for link switching or reselection without any separateinformation request to the AP MLD. The request message may includeinformation on the AP and information on the link to which the STA is tobe reconnected. When the AP MLD that has received the request messageaccepts the request, the AP MLD may transmit a response message of“Accept”. And, when the AP MLD rejects (or declines) the request, the APMLD may transmit a response message of “Decline”.

When the request is accepted, the AP may perform link (re)setup througha frame exchange with a link of a reselected AP starting from after theresponse message transmission. Conversely, when the request is declined,the STA may continue to use its initially connected link as it is.

An example of detailed AP MLD and non-AP MLD operations according to thegeneral method may be described with reference to FIG. 32 .

FIG. 34 shows operations of an AP MLD and a non-AP MLD for linkswitching or reconnection.

Referring to FIG. 34 , STA 2 may want to directly switch its link forreasons of ensuring QoS. If STA 2 has existing information received fromthe AP MLD (e.g., information received through a beacon frame ormanagement frame, and so on), or if STA 2 has already determined thelink it wishes to be reconnected to, STA 2 may request link switching orreconnection without any separate information request.

STA 2 may transmit STA information (e.g., STA ID, and so on) andinformation on the link that is intended to be switched (e.g., Link IDor AP BSS information, and so on) by including the correspondinginformation in a link switching request frame. When the AP MLD that hasreceived the request frame accepts the request, the AP MLD may transmit,to STA 3, a link switching response frame of “Accept” through theexisting Link 2. Thereafter, after performing a link (re)setup process,STA 2 of the non-AP MLD may be reconnected to AP 3.

Embodiment for Anchored Link Switching and Reconnection

According to an embodiment, an AP MLD may support an anchored link. Whenthe AP MLF supports an anchored link, additional detailed are consideredin the above-described embodiment for link switching and reconnection.

The AP MLD may support one anchored link or more than one anchoredlinks, and the AP MLD may provide information on the one anchored linkor more than one anchored links to a non-AP MLD through an anchored linklist information/element. The non-AP MLD may select one link or morethan one links from the above-described anchored link list and may usethe selected link(s). The remaining links that are not selected as theanchored link(s) may operate as non-anchored links.

The anchored link and the non-anchored link have a trade-off relation inthe aspect of power consumption and in the aspect of data load. That is,when the non-AP MLD uses one anchored link, the amount of powerconsumption may be reduced. However, it may be difficult to ensure data(most particularly, data for beacon and management frame) transmissionQoS. Conversely, when a plurality of anchored links are used, datatransmission QoS may be ensured. However, the amount of power reductionmay be reduced.

Therefore, the non-AP MLD should be capable of dynamically requestingreselection on an anchored link for efficient data exchange. Therefore,hereinafter, an embodiment for dynamically requesting anchored linkswitching/reselection, by a non-AP MLD may be proposed.

Firstly, an MLD structure supporting anchored link(s) may be describedwith reference to FIG. 35 .

FIG. 35 shows an example of an MLD structure supporting anchoredlink(s).

Referring to FIG. 35 , an AP MLD may use 2 links (i.e., AP 1 and AP 4)as anchored links among 5 links. A non-AP MLD may use one anchored linkby selecting Link 1 from the two links that are used as anchored links.The remaining links of the non-AP MLD may be connected to non-anchoredlinks (Link 2, Link 3). That is, the non-AP MLD should always performmonitoring on Link 1 for beacon and management frame reception.

According to an embodiment, STA 1 may request the anchored link it wasinitially used from the anchored link of AP 1 to the anchored link of AP4 for reasons of load balancing, and so on. In order to switch theanchored link, the above-described embodiment related to link switchingmay be applied.

However, among the links being supported by the AP MLD, the anchoredlink(s) is/are limited only to part of the links. Therefore, the AP MLDmay have a separate anchored link list. The non-AP MLD (or STA) shouldselect one link that is included in the anchored link list and may thenrequest for switching or reconnection. Additionally, since the non-APMLD should have at least one or more anchored links, when requesting forlink switching or reconnection, the non-AP MLD should request for theanchored link switching while considering this requirement.

For the above-described embodiment, the AP MLD is required toadditionally provide the non-AP MLD with “Anchored Link List”information. The aforementioned term “Anchored Link List” is merelyexemplary and may, therefore, be configured/expressed by using othervarious terms.

“Anchored Link List” (element/field): This is information on a list ofanchored links that are supported by the current AP MLD. For example,the information on the list of anchored links that are supported by thecurrent AP MLD may be indicated/configured as/of one or more Link IDs orAP BSS values, and so on. A Non-AP MLD should be connected to at leastone or more anchored lists, among the links included in the list.

The above-described information (e.g., “Anchored Link List”(element/field)) may be included in an existing beacon or managementframe and then transmitted, or, in case of the above-described solicitedmethod, the above-described information may be included in an inforesponse message and may be transmitted together to the non-AP MLD.

Therefore, in case the non-AP MLD requests for a switching of theanchored link that it is using, the non-AP MLD should be informed inadvance of the information on the currently supported anchored linklist. However, if the non-AP MLD is not informed of (or does not know)the anchored link list information or wishes to obtain the most recentinformation, the non-AP MLD may obtain the corresponding informationfrom the AP MLD by using the solicited method.

The STA may request for switching or reconnection to only one link inthe Anchored Link List. If the STA requests for switching orreconnection to another link that is not included in the list, the APMLD may transmit a reject message to the STA.

When requesting for an anchored link switching or reconnection, thereare details that should be considered in addition to the existing linkswitching method. A case where an STA of the non-AP MLD switches itsanchored list may be broadly divided into 2 cases.

A first case corresponds to a case where the STA that is alreadyconnected to an anchored link switches to another anchored link of theAP MLD (AP switch for an anchored link) for reasons of load balancing,and so on. A second case corresponds to a case where the STA that is(already) connected to an anchored link is disabled for reasons of powerstatus, and so on, and, therefore, another STA of the non-AP MLD isreconnected to the anchored link (STA switching for an anchored link).

The first case may operate similarly/identically as the above-describedembodiment for link switching and reconnection. However, whenreselecting the link, the STA should only select the link from theanchored link list that is supported by the AP MLD. In case of selectinganother link, the AP MLD may transmit a reject response message.

The second case needs additional consideration. The example for thesecond case may be described with reference to FIG. 34 .

FIG. 36 shows an example of a situation where anchored link switching orreconnection is needed.

Referring to FIG. 36 , in case of the STAs of the non-AP MLD, the stateof STA 1 may be disabled for various reasons (e.g., power off, and soon). At this point, since STA 2 and STA 3 are currently both connectedto non-anchored links, either one of the two STA should be reconnectedto an anchored link.

As shown in FIG. 36 , when the non-AP MLD is required to reconnect to ananchored link, the non-AP MLD may attempt to reconnect one STA, fromeither STA 2 or STA 3, to an anchored link.

For example, when the non-AP MLD knows (or has) the information on theanchored link list supported by the AP MLD, the non-AP MLD may select anappropriate link and may request link switching.

As another example, when the non-AP MLD does not have the information onthe anchored link list supported by the AP MLD, the non-AP MLD mayobtain the information through an info request to the AP MLD and may,then, select an appropriate link and request link switching.

An example of detailed AP MLD and non-AP MLD operations according to theabove-described embodiment may be described with reference to FIG. 37 .

FIG. 37 shows operations of an AP MLD and a non-AP MLD for anchored linkswitching or reconnection.

Referring to FIG. 37 , in case STA 1 that was connected to an anchoredlink is disabled, the non-AP MLD needs a new anchored link connection.At this point, the non-AP MLD may disconnect the initial connection ofSTA 3 to AP 3 via non-anchored link and may attempt reconnection to ananchored link.

For example, STA 3 may attempt connection to AP 1, which was initiallyused as an anchored link. As another example, STA 3 may attempt toestablish connection to a new AP 4, based on various information.

The process of selecting a new anchored link may be performedsimilarly/identically as the above-described embodiment for linkswitching and reconnection. For example, STA 3 may request reconnectionby selecting an anchored link that is recommended by the AP, or bydirectly selecting an anchored link by STA 3 itself. After completingthe anchored link reconnection, the link of STA 3 may operate as ananchored link.

Element/Field Including Information Related to an Anchored Link

According to an embodiment, when information related to an anchored linkthat is supported by the AP MLD is changed, or when the STA directlyrequest information on an anchored link, the AP MLD may transmit thecorresponding information (i.e., information related to the switchedanchored link or information related to an anchored link that is requestby the STA) to the non-AP MLD.

For example, the information may be included in a beacon frame asinformation related to an anchored link that is currently being used andmay then be transmitted, or the information may be included in aseparate management frame and may then be transmitted.

The information on an anchored link may include an “Anchored Link List”element indicating the above-described anchored link that is supportedby the AP MLD and information indicating usage or non-usage of ananchored link per STA.

Hereinafter, new elements including the above-described information onan anchored link may be proposed. The newly proposed element may beconfigured as described below.

1) “Anchored Link Indication” element (or field): An “Anchored LinkIndication” element may include information related to usage ornon-usage of an anchored link each of the STAs being connected to the APMLD. That is, the “Anchored Link Indication” element may be anelement/field indicating the usage or non-usage of an anchored link perlink or per STA of a non-AP MLD.

2) “STA ratio per Anchored Link” element (or field): An “STA ratio perAnchored Link” element may include information on a ratio or number ofSTA being connected per anchored link. Herein, however, only the STAsusing anchored links as their links may be considered. In other words,even if an AP MLD supports a first link as an anchored link, an STAusing the first link as a non-anchored link may not be included in theSTAs being connected to each anchored link (or STAs being connected peranchored link).

According to an embodiment, in all of the processes of theabove-described embodiment for anchored link switching or reconnection,when needed, the elements may be included in a frame as additionalinformation.

Detailed examples of the elements may be described with reference toFIG. 36 .

FIG. 38 and FIG. 39 respectively show detailed examples of elements foranchored link reconnection.

Referring to FIG. 38 and FIG. 39 , the information related to ananchored link may be transmitted through an Anchored Link List element(or field), an Anchored Link Indication element (or field), and/or anSTA ratio per Anchored Link element (or field). In other words, anelement for anchored link reconnection may include an Anchored Link Listelement (or field), an Anchored Link Indication element (or field),and/or STA ratio per Anchored Link element (or field).

According to an embodiment, as described above, the Anchored Link Listelement may include information on a list of links currently supportedby the AP MLD. For example, the information on the list of linkscurrently supported by the AP MLD may be indicated based on Link ID orAP BSS information, and so on. In other words, the list of linkscurrently supported by the AP MLD may be configured based on Link ID orAP BSS information.

According to an embodiment, the Anchored Link Indication element mayinclude information related to the usage or non-usage of an anchoredlink per STA of a non-AP MLD. For example, the information related tothe usage or non-usage of an anchored link per STA of a non-AP MLD maybe indicated through an indication bitmap per link (i.e., FIG. 36 ). Asanother example, the usage or non-usage of an anchored link for all STAsmay be indicated through one bitmap (i.e., FIG. 37 ).

As an example, when the information related to the usage or non-usage ofan anchored link is indicated by an indication bitmap according to linkIDs, the STA may verify the current anchored link(s) based on theAnchored Link List element value. Therefore, the STA may verify theratio of STAs being connected to each anchored link. At this point, theIndication bitmap field for a non-anchored link may be omitted in orderto reduce overhead.

In the bitmap, when the value of one of the bits is equal to 1, the onebit may denote that the link currently connected to the STA is ananchored link. When the value of one of the bits is equal to 0, the onebit may denote that the link currently connected to the STA is anon-anchored link. The embodiment wherein a bitmap is used in order toindicate the connection or non-connection of an anchored link per STA ismerely exemplary. And, therefore, the information related to theconnection or non-connection of an anchored link per STA may betransmitted through other various embodiments.

According to an embodiment, a ratio of STAs for all links beingsupported by the AP MLD may also be transmitted. According to anembodiment, the STA ratio per Anchored Link element may includeinformation on a usage ratio or number of actual anchored links of theSTA per anchored link. For example, by having the information indicatedonly for the anchored link(s) that are indicated in the Anchored LinkList element, this has an effect of reducing overhead.

An example of configuring a value of the STA ratio per Anchored Linkelement may hereinafter be described.

For example, the AP MLD may include 5 APs (i.e., AP 1 to AP 5), and AP 1may be connected to STAs through Link 1. AP 2 may be connected to STAsthrough Link 2. AP 3 may be connected to STAs through Link 3. AP 4 maybe connected to STAs through Link 4. And, AP 5 may be connected to STAsthrough Link 5.

The AP MLD may support 2 links, among 5 links (i.e., Link 1 to Link 5),as anchored links. Link 1 and Link 4 may be supported/used as anchoredlinks.

A total of 10 STAs may be connected to Link 1 (or AP 1), and 7 STAs mayuse Link 1 as the anchored link. This may be expressed as a ratio of70%, and this may be expressed as a value of 7.

A total of 20 STAs may be connected to Link 4 (or AP 4), and 5 STAs mayuse Link 4 as the anchored link. This may be expressed as a ratio of25%, and this may be expressed as a value of 5.

By having the STA ratio per Anchored Link element transmitted togetherwith the above-described STA ratio per Link element information, moreaccurate information may be transmitted to the STA. Generally, since ananchored link may have a relatively larger amount of data traffic ascompared to a non-anchored link, the STA ratio per Anchored Link elementmay be used as useful information for an STA intending to reselect itsanchored link.

The non-AP MLD may verify whether or not the link to which the non-APMLD is connected is an anchored link, a connection ratio of STAs peranchored link, and a ratio of anchored links that are actually beingused, based on the above-described information (or elements).

Additionally, when the AP MLD transmits information on other links.i.e., all links, through the above-described elements, the STA mayverify the connection ratio and actual usage ratio of each STA for allanchored links of the AP MLD, based on one frame. Therefore, theinformation (or elements) may be used when the STA reselects theanchored link that it intends to use.

Therefore, according to the embodiment for anchored link switching orreselection, by not only using the various link information (e.g.,information on BSS load per AP or information on STR capability perlink, and so on) used in the embodiment for link switching orreselection but also using the above-described information on anchoredlinks (e.g., Anchored Link List information, information indicating theusage or non-usage of an anchored link per STA, or information on actualSTA usage ratio per anchored link, and so on), a more appropriateanchored link switching or reconnection may be performed.

Signaling for Indicating a Link Switching and Reconnection Method

In order to indicate the methods proposed above, an agreement processbetween an AP MLD and a non-AP MLD may be needed through a negotiationbetween the AP MLD and the non-AP MLD. For this, a signaling method forenabling the methods that will hereinafter be proposed in the presentspecification may be proposed.

Firstly, in order to indicate the methods that are proposed above, a newelement may be proposed. Hereinafter, although an embodiment related tosignaling for indicating a link switching and reconnection method willbe described, the corresponding embodiment may also be applied to anembodiment related to signaling for indicating an anchored linkswitching and reconnection method.

The signaling process for indicating a link switching and reconnectionmethod may be performed during multi-link setup or after multi-linksetup. Additionally, the new elements that will hereinafter be proposedmay be used in the signaling process for indicating a link switching andreconnection method. For example, the elements may be included in a(re)association frame of the related art specification or in a newframe.

Information Obtain Method (IOM) Capability Element

An IOM Capability Element may include information related to enabling ordisabling of a method for additionally obtaining information for amulti-link. For example, in a process of exchanging messages for anoperation negotiation (or agreement) (e.g., a capability negotiationprocess) between an AP MLD and a non-AP MLD during a multi-link setupprocess, an IOM capability value may be present in an element of themessage. And, the presence of an IOM capability value in an element ofthe message may denote that the IOM capability is supported.

According to an embodiment, when the AP MLD supports the IOM capability,an AP may be provided with internally shared information of other AP andmay have (or possess) information of other AP. The MLD that does nothave any shared information of other AP cannot support the IOMcapability.

According to an embodiment, when the value of the IOM capability elementis configured to a first value (e.g., 1), this may mean that the IOMcapability element enables the IOM and that the IOM is operated by usingthe indicated capability. Conversely, when the value of the IOMcapability element is configured to a second value (e.g., 0), this maymean that IOM capability element disables the IOM.

According to the embodiment, the IOM capability element may includevarious fields/elements for indicating various operations. For example,the IOM capability element may also include various fields/elements thatwill hereinafter be described. However, depending upon a case where theAP MLD requests link switching and a case where the non-AP MLD requestslink switching, the fields/elements that are added to the IOM capabilityelement may be differently configured. Additionally, among thefields/elements that are added to the IOM capability element, at leastpart of the fields/elements may be omitted. For example, among thefields/elements that are added to the IOM capability element,fields/elements that include information that does not need to beindicated may be omitted.

Hereinafter, examples of various fields/elements beingdefined/configured for obtaining additional information related to amulti-link may hereinafter be described. The various fields/elementsthat will hereinafter be described may be independently configured, ortwo or more fields/elements may be combined, and may then be transmittedthrough various frames.

Method Type (or Method) Field/Element

A Method Type field/element (hereinafter referred to as Methodfield/element) may include information related to an operation method ofan IOM. In other words, the Method field/element may indicate anoperation method of the IOM. For example, when a non-AP MLD enables (oractivates) an IOM method for obtaining information from an AP, thenon-AP MLD may select and indicate a method that is to be used, amongthe methods proposed above (e.g., solicited method, unsolicited method,general method).

For example, the solicited method may be indicated/used, based on thevalue of the Method field/element being equal to a first value (e.g.,0). The unsolicited method may be indicated/used, based on the value ofthe Method field/element being equal to a second value (e.g., 1). Thegeneral method may be indicated/used, based on the value of the Methodfield/element being equal to a third value (e.g., 2). And, both thesolicited method and the unsolicited method may be indicated/used, basedon the value of the Method field/element being equal to a fourth value(e.g., 3).

As another example, 1 bit may be used as the Method field/element. Inthis case, the solicited method may be indicated/used, based on thevalue of the Method field/element being equal to a first value (e.g.,0). The unsolicited method may be indicated/used, based on the value ofthe Method field/element being equal to a second value (e.g., 1).

As another example, 2 bits may be used as the Method field/element. Inthis case, single usage or multiple usage of each method may beindicated.

Info Range Field/Element

An Info range field may be used for indicating the range of information,when information is provided to a non-AP MLD via IOM. In other words,the Info range field may include information related to the informationrange, when information is provided to the non-AP MLD via IOM.

For example, when a value of the Info range field is equal to a firstvalue (e.g., 0), the Info range field may indicate that only part of theinformation is provided. And, when a value of the Info range field isequal to a second value (e.g., 1), the Info range field may indicatethat all of the information (or the whole information) is provided.

According to an embodiment, a subfield for indicating the range ofinformation that is to be provided (e.g., all information or partialinformation) may also be included in the Info range field. For example,a subfield for indicating the range of information that is to beprovided may be defined/configured as all/partial subfields.

According to an embodiment, a subfield for indicating whether allinformation is to be provided or whether only changed information amongall of the information is to be provided may be newly proposed. In otherwords, the newly proposed subfield may indicate whether all informationis to be provided or whether only changed information among all of theinformation is to be provided.

For example, the subfield for indicating whether all information is tobe provided or whether only changed information among all of theinformation is to be provided may be defined/configured as an onlyupdated subfield.

When the STA wishes to receive only the changed (or updated)information, a value of the only updated subfield may be configuredas 1. In other words, when the STA wishes to receive only the changed(or updated) information, the STA may set the only updated subfieldvalue to 1. For example, in case of the solicited method, when the STArequests information, the AP (or AP MLD) may transmit only the changedinformation (i.e., updated information), among the requestedinformation. As another example, in case of the unsolicited method, theAP may notify only the changed information in the information range (orinfo range) that is configured by the STA.

According to the above-described example, in order to receive only thechanged information, an only updated subfield has been proposed withinthe Info range field. However, the present disclosure will not belimited only to this. And, therefore, in order to receive only thechanged information, a separate field or element may bedefined/configured.

According to the above-described embodiment, a range of the informationthat may be requested by the STA may be configured as updatedinformation or all information. In this case, the STA, which does notwish a large amount of frame overhead, may request reception of only thechanged information. Therefore, various overhead may be reduced.

Link Condition Field/Element

Link condition field may be used for indicating a specific link that isbeing requested. In other words, the Link condition field may includeinformation on a specific link that is being requested. The Linkcondition field may be used when the STA wishes to received only theinformation on a specific link from the AP.

The Link condition field may be marked (or indicated) by a linkidentifier (e.g., Link ID, BSS ID). In other words, the Link conditionfield may include information related to a link identifier (e.g., LinkID, BSS ID). In other words, in order to specify a link for obtaininginformation, a link identifier may be used.

For example, when an STA being connected to Link 1 wishes to requestonly the information on Link 2 and Link 3, to the AP, the STA mayindicate Link 2 and Link 3 to the Link condition field, so as to requestinformation on Link 2 and Link 3 to the AP. For example, when theabove-described info range field value is equal to 1, all informationcorresponding to Link 2 and Link 3 may be transmitted. As anotherexample, when the above-described info range field value is equal to 0,only partial information designated by the STA in Link 2 and Link 3 maybe transmitted. According to an embodiment, the partial informationdesignated by the STA may be determined through the Info conditionfield, which will be described below.

According to an embodiment, when there is no Link condition field value,or when the Link condition field value is equal to 0, the AP maydetermine that there is no link condition. Therefore, the AP mayprovide/transmit information related to all links to the STA.

Info Condition Field/Element

The Info condition field may be used for indicating a specificinformation type that is being requested. In other words, the Infocondition field may be used in a case where the STA wishes to receiveonly specific information from the AP.

For example, the Info condition field may be used only when the Inforange field is set to 0. As another example, the Info condition fieldmay be used to allow the STA to indicate specific information even whenthere is no info range field.

For example, information that can be designated by the STA (e.g., BSSLoad, STR Capability, and so on) may be indicated by a bitmap, withinthe Info condition field. For example, the type of information indicatedby the AP, indication method or order within a bit, and so on, may bevariously configured.

According to an embodiment, the Info condition field may be usedtogether with the above-described Link condition field. According to anembodiment, the Info condition field may transmit request information ofvarious conditions to the STA (or AP) based on a combination of variousfields/elements.

According to an embodiment, in order to allow the STA to requestspecific information, an element of the existing specification may bere-used. For example, in order to allow the STA to request specificinformation, a Request IE or an Extended Request IE may be used.Hereinafter, a detailed example of the Request IE or Extended Request IEmay be described.

FIG. 40 shows a detailed example of a Request element format.

Referring to FIG. 40 , a Request element may include an element IDfield, a length field, and/or a Requested Element IDs field. Forexample, the element ID field may include information indicating thatthe element is a request element. The length field may includeinformation related to a number of octets after the length field. TheRequested Element IDs field may include information on an element IDthat is to be requested.

FIG. 41 shows a detailed example of an Extended Request element format.

Referring to FIG. 40 , an Extended Request element may include anelement ID field, a length field, an Element ID extension field, aRequested Element ID field, and/or a Requested Element IDs Extensionsfield. The element ID field and the length field may be configuredsimilarly as the element ID field and the length field of FIG. 40 . TheElement ID extension field may be combined with the Element ID field, soas to configure the Extended Element ID. The Requested Element ID fieldmay include one of the element IDs that are used for indicating theextended element. The Requested Element IDs Extensions field may includean element ID extension value of 1 octet.

Referring to FIG. 40 and FIG. 41 , the element (request element orExtended Request element) may be used for requesting specificinformation to a probe request frame or an information request frame.

For example, when the STA indicates a list of information for which itwishes to receive a response by using requested element IDs, the AP mayinclude and transmit the corresponding information in a probe responseframe or an information response frame.

Therefore, according to the embodiment of the present specification, theelement (request element or Extended Request element) may be reused/usedas an indicator for requesting specific information. For example, theelement may be used for requesting wanted information of a wanted linktogether with a link identifier (e.g., Link identifier).

For example, in order to request BSS load information of AP 2, the STAmay use a request element and Link identifier. The STA may include anelement ID for the BSS load information through the Request element.And, the STA may indicate AP 2 through the Link identifier. Therefore,the STA may request BSS load information of AP 2 based on the Requestelement and the Link identifier.

According to an embodiment, the above-described element ID informationmay be used for indicating specific information of a specific AP throughvarious combinations along with (or together with) Link identifierinformation. According to an embodiment, even in a case where a newframe for requesting information is defined, instead of an existingframe, the above-described Request element and/or Extended Requestelement may be used/reused.

In the prior art specification, a PV1 Probe Response Option element wasused in order to request specific information. Therefore, in anembodiment for indicating specific information, a PV1 Probe ResponseOption element may be used.

FIG. 42 shows a detailed example of a PV1 Probe Response Option elementformat.

Referring to FIG. 42 , a PV1 Probe Response Option element may be usedfor requesting optional information by using information wanted by theSTA as a Probe request. For frequently used information, each set ofinformation may be indicated by using a Probe response option bitmap.

However, the EHT specification should be capable of providinginformation of a multi-link while considering an MLD. Therefore, the STAmay request specific information of various combinations of specificlinks by using a bitmap indicator along with a link identifier, as shownin Table 21 to Table 26.

According to an embodiment, in the EHT specification, optionalinformation (e.g., STR capability) may be newly defined along with amulti-link. Therefore, when the PV1 Probe response option element isused/re-used, bitmaps for information that needs to be newly defined oradditionally obtained may be newly defined or additionally defined inthe EHT specification. The Probe response option bitmap may beconfigured as shown below in Table 21 to Table 26.

When an i-th bit of the Probe response group bitmap is configured as 1,probe response option bitmap subfield i may be included in the PV1 ProbeResponse Option element.

Table 21 shows an example of Probe Response Option Bitmap subfield 0.

Table 22 shows an example of Probe Response Option Bitmap subfield 1.

Table 23 shows an example of Probe Response Option Bitmap subfield 2.

Table 24 shows an example of Probe Response Option Bitmap subfield 3.

Table 25 shows an example of Probe Response Option Bitmap subfield 4.

Table 26 shows an example of Probe Response Option Bitmap subfield 5.

TABLE 21 Bit Position Subfield Item requested Reference 0 Request FullSSID Full SSID element if the bit SSID element and PV1 Probe is set to1, and Compressed Response frame format SSID field if the bit is set to0 1 Request Next TBTT Next TBTT field PV1 Probe Response frame format 2Request Access Network Access Network Options Interworking elementOptions field 3 Request S1G Beacon S1G Beacon Compatibility S1G BeaconCompatibility Compatibility element element 4 Request Supported RatesSupported Rates and BSS Supported Rates and Membership Selectors BSSMembership Selectors element element 5 Request S1G Capability S1GCapabilities element S1G Capabilities element 6 Request S1G OperationS1G Operation element S1G Operation element 7 Request RSN RSN elementRSNE

TABLE 22 Bit Position Subfield Item requested Reference 0 Request RPSRPS element RPS element 1 Request Page Slice Page Slice element PageSlice element 2 Request TSF Timer TSF Timer Accuracy TSF Timer Accuracyelement Accuracy element 3 Request S1G Relay S1G Relay Discovery S1GRelay Discovery element Discovery element 4 Request S1G Sector S1GSector Operation S1G Sector Operation Operation element element 5Request Short Beacon Short Beacon interval Short Beacon IntervalInterval element element 6-7 Reserved

TABLE 23 Bit Position Subfield Item requested Reference 0 RequestCountry Country element Country element 1 Request Power Constraint PowerConstraint element Power Constraint element 2 Request TPC Report TPCReport element TPC Report element 3 Request Extended Extended SupportedRates Extended Supported Rates Supported Rates element and BSSMembership Selectors element 4 Request Extended Extended CapabilitiesExtended Capabilities Capabilities element element 5 Request BSS LoadBSS Load element BSS Load element 6 Request EDCA EDCA Parameter Set EDCAParameter Set element Parameter Set element 7 Request SupportedSupported Operating Supported Operating Operating Classes Classeselement Classes element

TABLE 24 Bit Position Subfield Item requested Reference 0 RequestMeasurement Measurement Pilot MeasurementPilot Pilot TransmissionTransmission element Transmission element 1 Request Multiple BSSIDMultiple BSSID element Multiple BSSID element 2 Request RM Enabled RMEnabled Capabilities RM Enabled Capabilities Capabilities elementelement 3 Request AP Channel AP Channel Report AP Channel Report elementReport element 4 Request BSS Average BSS Average Access Delay BSSAverage Access Delay Access Delay element element 5 Request AntennaAntenna element Antenna element 6 Request BSS Available BSS AvailableAdmission BSS Available Admission Admission Capacity Capacity elementCapacity element 7 Request BSS AC BSS AC Access Delay BSS AC AccessDelay Access Delay element element

TABLE 25 Bit Position Subfield Item requested Reference 0 RequestMobility Mobility Domain element Mobility Domain element Domain 1Request QoS Traffic QoS Traffic Capability QoS Traffic CapabilityCapability element element 2 Request Channel Usage Channel Usage elementChannel Usage element 3 Request Time Time Advertisement TimeAdvertisement Advertisement element element 4 Request Time Zone RequestTime Zone Request Time Zone element element 5 Request IBSS IBSSParameter Set IBSS Parameter Set element Parameter Set element 6-7Reserved Reserved

TABLE 26 Bit Position Subfield Item requested Reference 0 RequestInterworking Interworking element Interworking element 1 RequestAdvertisement Advertisement Protocol Advertisement Protocol Protocolelement element 2 Request Roaming Roaming Consortium Roaming ConsortiumConsortium element element 3 Request Emergency Emergency AlertIdentifier Emergency Alert Identifier Alert Identifier element element 4Request QLoad Report QLoad Report element QLoad Report element 5 RequestMulti-band Multi-band element Multi-band element 6 Request Multiple MACMultiple MAC Sublayers Multiple MAC Sublayers Sublayers element element7 Request Reduced Reduced Neighbor Report Reduced Neighbor ReportNeighbor Report element element

According to an embodiment, in order to request specific information ona multi-link, Probe Response Option Bitmap subfield 6 or 7 may be newlydefined/configured.

Transmission Periodic Field/Element

When the STA wishes to receive information by using the unsolicitedmethod, whether the STA is to periodically receive or aperiodicallyreceive a message including the information may be indicated through theTransmission periodic field.

For example, when the STA wishes to receive the informationaperiodically, the AP may inform updated information each time an updateoccurs in the information of another AP.

As another example, when the STA indicates the information to beperiodically received, a message including the information may bereceived at a periodic interval that is configured by the STA.

According to the embodiment, the transmission periodic field may beconfigured on 1 bit. When the value of the transmission periodic fieldis set to 1, the STA may receive/obtain information through a periodicmethod, which periodically receives a message. When the value of thetransmission periodic field is set to 0, the STA may receive/obtaininformation through an aperiodic method, which aperiodically receives amessage.

Transmission Interval Field/Element

According to an embodiment, when the STA wishes to periodically receiveinformation of another AP, the STA may directly configure the interval(or transmission cycle period). The STA may transmit information on aninterval at which information on another AP is to be received, based onthe transmission interval field. Herein, however, the interval should beconfigured to be shorter than the beacon transmission interval. Forexample, when the FILS Discovery frame is used, the interval should beconfigured as 20 us.

As described above, a transmission interval may be defined as a separatefield within an element indicating the transmission interval, and mayalso be defined as a subfield within the transmission periodic field.

According to an embodiment, a field/element that is defined/configuredfor obtaining additional information related to a multi-link will not belimited to the above-described field/element, and other variousfield(s)/element(s) may be further configured.

Therefore, during the multi-link setup process, the MLD (AP MLD ornon-AP MLD) may use at least one of the above-described elements/fieldsso as to indicate an IOM capability through a negotiation between the APMLD and the non-AP MLD. Additionally, after completing the multi-linksetup process, the MDL may update the negotiation details between theMLDs through a separate message exchange.

According to an embodiment, when the IOM capability is enabled, the APMLD and the non-AP MLD may operate based on the embodiment for the linkswitching and reconnection.

Hereinafter, exemplary operations of the AP MLD and the non-AP MLD whenthe IO capability is enabled may be described. For example, by havingthe non-AP MLD transmit the above-described fields/elements to the APMLD, the non-AP MLD may request additional information for a multi-linkto the AP MLD. The non-AP MLD may transmit the above-describedfields/elements including the IOM Capability element to the AP MLD. Thefields/elements including the IOM Capability element is merelyexemplary. And, therefore, the IOM Capability element may also betransmitted through an independent field/element.

For example, during a multi-link setup process, the non-AP MLD maytransmit an IOM Capability element including “Method field=0” and “Inforange field=1” to the AP MLD, and the non-AP MLD may negotiate this withthe AP MLD. In this case, the non-AP MLD may operate by using thesolicited method, after the multi-link setup. Then, when requestinginformation, the non-AP MLD may request information for a multi-link(e.g., information on other AP) including all information being includedin a beacon. Therefore, the AP MLD may provide/transmit information on alink to a response message only when the AP MLD has received a requestmessage from the STA. When receiving the request message, the AP MLD maytransmit a response message including information on all links withinthe AP MLD to the STA. The information on all links within the AP MLDmay include all information included in a beacon.

As another example, the non-AP MLD may transmit an IOM Capabilityelement including “Method field=1”, “Info range field=0”, “Linkrange=Link id 2”, “Info condition field=(value indicating BSS loadthrough bitmap)” to the AP MLD, and the non-AP MLD may negotiate thiswith the AP MLD. In this case, the non-AP MLD may operate by using theunsolicited method, after the multi-link setup. Therefore, the AP maytransmit BSS load information of Link 2 to the STA through a separatemessage, even without a separate request message.

As yet another example, the non-AP MLD may transmit an IOM Capabilityelement including “Method field=0”, “Info range field=0”, “only updatedfield or subfield=1”, “Info condition field=(value indicating BSS loadthrough bitmap)” to the AP MLD, and the non-AP MLD may negotiate thiswith the AP MLD. In this case, the non-AP MLD may operate by using thesolicited method, after the multi-link setup. Therefore, the AP MLD (orAP) may include only the updated (or changed) information, among the BSSload information of all APs of the AP MLD, which was connected at thetime the STA requested the information, in a response message, and maythen transmit the message to the STA.

According to an embodiment, the AP MLD and the non-AP MLD may enable theIOM method, which is proposed through the signaling method proposed inthe present specification, during the multi-link setup or after themulti-link setup. Additionally, the AP MLD and the non-AP MLD mayrestrict (or limit) the range and type of the requested informationthrough various field values within the IOM Capability element.

According to an embodiment, although the IOM operation may be performedafter establishing an accurate operation negotiation between the MLDsthrough the above-described IOM signaling method, the IOM operation mayalso be performed by an MLD implementation without any separatesignaling process. This may mean that the IOM may be operated by an APMLD implementation or a non-AP MLD implementation without anynegotiation between the AP MLD and the non-AP MLD.

Based on the above-described embodiments, although the AP MLD and thenon-AP MLD may operate, when an MLD performs the IOM operation withoutany separate signaling exchange, the following restrictions may occur.

1) Restrictions on the solicited method: When info sharing between APsof the AP MLD is not supported, and when the STA has requestedinformation on another link, response cannot be made (or transmitted).

2) Restrictions on the unsolicited method: the AP may autonomouslydetermine the STA that needs additional link information and may providea separate message (e.g., beacon interval, and so on) to thecorresponding STA. Therefore, the STA cannot predict whether or not toreceive this information.

When the MLD implements an IOM without any separate signaling method,the operation process may be simplified. However, the above-describedrestrictions may occur.

According to an embodiment, a method for requesting information relatedto a multi-link may be configured based on a negotiation between an APMLD and a non-AP MLD that is performed by using the above-described IOMcapability element. On the other hand, in case of the solicited method,the STA may indicate specific information other than the negotiatedinformation and may temporarily wish to obtain the correspondinginformation. In this case, when the STA dynamically sends a requestmessage, the request may be made while including the indications (e.g.,IOM capability information).

For example, during the multi-link setup or after the multi-link setup,although the ST may receive information the AP based on the negotiateddetails according to the negotiation between the AP MLD and the non-APMLD, the STA may temporarily wish to request information of a specificAP or specific parameter information of APs. In this case, whenrequesting information, the STA may include instructions on theinformation, which the STA wishes to request, in the “IOM capability”element within the request frame (e.g., probe request frame or(re)association frame or new frame, and so on) and may transmit therequest frame. The AP may transmit/provide a response message includingthe information, which the STA wishes to request, to the STA based onthe request frame. According to the embodiment, when a field within theIOM capability element is omitted, the AP may provide information to theSTA based on previously (or existing) negotiated details.

Therefore, during the multi-link setup process or after the multi-linksetup process, the MLD (AP MLD or non-AP MLD) may use theabove-described element so as to perform a negotiation between the APMLD and the non-AP MLD. The non-AP MLD may perform a negotiation on theinformation that is to be provided (or information that is to bereceived), based on the negotiation, and may then receive thecorresponding information. Additionally, by including instructions ofthe information, for which the STA wishes to receive a request, in therequest message, and transmitting the request message, the STA maytemporarily receive only the requested information. Herein, however,when the specific instructions are omitted from the request message, thenon-AP MLD and the AP MLD may operate based on the previously (orexisting) negotiated instructions.

According to an embodiment, when the non-AP MLD and the AP MLD wish tochange the negotiated details after completing the multi-link setup, thenon-AP MLD and the AP MLD may update the negotiated details between theMLDs through a separate message exchange.

FIG. 43 is a flowchart describing operations of a multi-link device.

Referring to FIG. 43 , in step S4310, a multi-link device (MLD) maytransmit a request frame including an information field for requestingcomplete elements included in an element set that is designated for asecond link. According to an embodiment, the multi-link device (MLD) maytransmit a request frame including an information field for requestingcomplete elements included in an element set that is designated for asecond link, to a first AP of an access point (AP) multi-link device,through a first STA.

For example, the multi-link device may be connected to an AP multi-linkdevice through a plurality of links including a first link. Themulti-link device may include a plurality of STAs related to theplurality of links. For example, among the plurality of STAs, the firstSTA may be connected to the first link. In other words, the first STAmay operate on the first link. Additionally, the first STA may beconnected to a first AP of the AP multi-link device through the firstlink.

For example, the plurality of links and a second link may be includedwithin 2.4 GHz, 5 GHz, and 6 GHz bands.

According to an embodiment, the request frame may include identifier(ID) information on the second link. The identifier information on thesecond link may be configured of 4-bit information. For example, anidentifier for the first link and an identifier for the second link maybe expressed in 4 bits.

According to an embodiment, a set of elements that may be requestedthrough the request frame may be referred to as an element set.Therefore, complete elements included in the element set may meancomplete elements that may be requested through the request frame. Inother words, the multi-link device may request all information relatedto the second link based on the request frame.

For example, an element set that is designated for the second link mayinclude an element related to a capability of the second link or anelement related to a parameter of the second link.

According to an embodiment, the request frame may include first bitinformation for indicating that complete elements included in thedesignated element set are requested. In other words, an informationfield for requesting complete elements included in the element setdesignated for the second link may be configured as 1-bit information.

For example, the 1-bit information may be configured to have a firstvalue. In other words, by configuring the 1-bit information as a firstvalue (e.g., 1), the multi-link device may indicate that completeelements included in the designated element set are requested.

Additionally, by configuring the 1-bit information as a second value(e.g., 0), the multi-link device may indicate that part of the elements(or partial elements) included in the designated element set arerequested.

According to an embodiment, the request frame may further include aninformation field for requesting complete elements included in anelement set designated for a third link, among the plurality of links.That is, the multi-link device may request complete elements included inthe element set designated for the second link and complete elementsincluded in the element set designated for the third link through therequest frame.

In step S4320, the multi-link device may receive a response frame, basedon the request frame. According to an embodiment, the multi-link devicemay receive the response frame from the first AP through the first STA,based on the request frame.

According to an embodiment, the response frame may include completeelements included in the element set designated for the second link.

According to an embodiment, the second link may be differentiated fromthe plurality of links. When the second link is differentiated from theplurality of links, the multi-link device may transmit the request framefor requesting elements related to a link that is currently notconnected to the multi-link device. The multi-link device may receivethe elements related to the link that is currently not connected to themulti-link device through a response frame, based on the request frame.

The multi-link device may transmit a second request frame for requestingthe link connected to the first STA to be switched from the first linkto the second link, based on the response message. Thereafter, themulti-link device may perform a procedure of switching the link that isto be connected to the first STA from the first link to the second link,based on the second request frame.

The multi-link device may establish a connection between the first STAand a second AP of the AP multi-link device, based on the procedure forswitching the link connected to the first STA from the first link to thesecond link. For example, the second AP may operate on the second link.Additionally, the first STA may also operate on the second link. Inother words, the first STA may establish a connection with the second APthrough the second link, based on the above-described procedure.

According to an embodiment, the second link may be included in theplurality of links. When the second link is included in the plurality oflinks, the multi-link device may transmit the request frame forrequesting elements related to the link that is currently connected tothe multi-link device through the first link. In other words, themulti-link device may transmit a request frame for requesting elementsrelated to another link through the first link. The multi-link devicemay receive elements related to a link excluding the first link, amongthe links currently connected to the multi-link device, through aresponse frame, based on the request frame.

FIG. 44 is a flowchart describing operations of an AP multi-link device.

Referring to FIG. 44 , an AP multi-link device (MLD) may receive arequest frame including an information field for requesting completeelements included in an element set that is designated for a secondlink. According to an embodiment, the AP multi-link device (MLD) mayreceive a request frame including an information field for requestingcomplete elements included in an element set that is designated for asecond link, to a first STA of a multi-link device, through a first AP.

According to an embodiment, the AP multi-link device may be connected toa multi-link device through a plurality of links. For example, a secondlink may be included in the plurality of links. As another example, thesecond link may be differentiated from the plurality of links.

For example, the AP multi-link device may be connected to the multi-linkdevice through a plurality of links including a first link. The APmulti-link device may include a plurality of APs related to theplurality of links. For example, among the plurality of APs, the firstAP may be connected to the first link. In other words, the first AP mayoperate on the first link. Additionally, the first AP may be connectedto the first STA of the multi-link device through the first link.

For example, the plurality of links and a second link may be includedwithin 2.4 GHz, 5 GHz, and 6 GHz bands.

According to an embodiment, the request frame may include identifier(ID) information on the second link. The identifier information on thesecond link may be configured of 4-bit information. For example, anidentifier for the first link and an identifier for the second link maybe expressed in 4 bits.

According to an embodiment, a set of elements that may be requestedthrough the request frame may be referred to as an element set.Therefore, complete elements included in the element set may meancomplete elements that may be requested through the request frame.

For example, an element set that is designated for the second link mayinclude an element related to a capability of the second link or anelement related to a parameter of the second link.

According to an embodiment, the request frame may include first bitinformation for indicating that complete elements included in thedesignated element set are requested. In other words, an informationfield for requesting complete elements included in the element setdesignated for the second link may be configured as 1-bit information.

For example, the 1-bit information may be configured to have a firstvalue. In other words, by configuring the 1-bit information as a firstvalue (e.g., 1), the multi-link device may indicate that completeelements included in the designated element set are requested.

Therefore, the AP multi-link device may verify that the multi-linkdevice has requested complete elements included in the designatedelement set, based on the 1-bit information.

According to an embodiment, the request frame may further include aninformation field for requesting complete elements included in anelement set designated for a third link, among the plurality of links.

In step S4420, the AP multi-link device may transmit a response frame,based on the request frame. According to an embodiment, the APmulti-link device may transmit the response frame to the first STAthrough the first AP, based on the request frame.

According to an embodiment, the response frame may include completeelements included in the element set designated for the second link.

According to an embodiment, the second link may be differentiated fromthe plurality of links. When the second link is differentiated from theplurality of links, the AP multi-link device may receive the requestframe for requesting elements related to a link that is currently notconnected to the AP multi-link device. The AP multi-link device maytransmit the elements related to the link that is currently notconnected to the AP multi-link device through a response frame, based onthe request frame.

According to an embodiment, the AP multi-link device may receive asecond request frame for requesting the link connected to the first STAto be switched from the first link to the second link, based on theresponse message. Thereafter, the AP multi-link device may perform aprocedure of switching the link that is to be connected to the first STAfrom the first link to the second link, based on the second requestframe.

A second AP of the AP multi-link device may establish a connection withthe first STA, based on the procedure for switching the link connectedto the first STA from the first link to the second link. For example,the second AP may operate on the second link. Additionally, the firstSTA may also operate on the second link. In other words, the first APmay establish a connection with the first STA through the second link,based on the above-described procedure.

According to an embodiment, the second link may be included in theplurality of links. When the second link is included in the plurality oflinks, the AP multi-link device may receive a request frame forrequesting elements related to remaining links excluding the first linkthrough the first link, among the plurality of links. The AP multi-linkdevice may transmit elements related to the links excluding the firstlink, among the links currently connected to the AP multi-link device,through a response frame, based on the request frame.

The above-described technical features of the present specification maybe applied to various device and methods. For example, theabove-described technical features of the present specification may beperformed/supported through FIG. 1 and/or FIG. 19 . For example, theabove-described technical features of the present specification may beapplied to only part of FIG. 1 and/or FIG. 19 . For example, theabove-described technical features of the present specification may beimplemented based on the processing chip(s) (114, 124) of FIG. 1 , orimplemented based on the processor(s) (111, 121) and the memory(s) (112,122), or implemented based on the processor (610) and the memory (620)of FIG. 19 . For example, a device of the present specification mayinclude a processor, and a memory being operatively connected to theprocessor, wherein the processor may be configured to transmit a requestframe including an information field for requesting complete elementsincluded in an element set designated for a second link to a firstaccess point (AP) of an AP multi-link device, through a first station(STA) operating on a first link, and to receive a response frame fromthe first AP through the first STA, based on the request frame, whereinthe response frame includes complete elements included in the elementset designated for the second link.

The technical features of the present specification may be implementedbased on a computer readable medium (CRM). For example, the CRM that isproposed in the present specification may encoded as at least onecomputer program including instructions. When executed by at least oneprocessor, the instructions may perform operations including the stepsof transmitting a request frame including an information field forrequesting complete elements included in an element set designated for asecond link to a first access point (AP) of an AP multi-link device,through a first station (STA) operating on a first link, and receiving aresponse frame from the first AP through the first STA, based on therequest frame, wherein the response frame includes complete elementsincluded in the element set designated for the second link. Theinstructions that are stored in the CRM of the present specification maybe executed by at least one processor. At least one processor beingrelated to the CRM of the present specification may be the processor(s)(111, 121) or processing chip(s) (114, 124) of FIG. 1 , or the processor(610) of FIG. 19 . Meanwhile, the CRM of the present specification maybe the memory(s) (112, 122) of FIG. 1 , or the memory (620) of FIG. 19 ,or a separate external memory/storage medium/disc, and so on.

The foregoing technical features of this specification are applicable tovarious applications or business models. For example, the foregoingtechnical features may be applied for wireless communication of a devicesupporting artificial intelligence (AI).

Artificial intelligence refers to a field of study on artificialintelligence or methodologies for creating artificial intelligence, andmachine learning refers to a field of study on methodologies fordefining and solving various issues in the area of artificialintelligence. Machine learning is also defined as an algorithm forimproving the performance of an operation through steady experiences ofthe operation.

An artificial neural network (ANN) is a model used in machine learningand may refer to an overall problem-solving model that includesartificial neurons (nodes) forming a network by combining synapses. Theartificial neural network may be defined by a pattern of connectionbetween neurons of different layers, a learning process of updating amodel parameter, and an activation function generating an output value.

The artificial neural network may include an input layer, an outputlayer, and optionally one or more hidden layers. Each layer includes oneor more neurons, and the artificial neural network may include synapsesthat connect neurons. In the artificial neural network, each neuron mayoutput a function value of an activation function of input signals inputthrough a synapse, weights, and deviations.

A model parameter refers to a parameter determined through learning andincludes a weight of synapse connection and a deviation of a neuron. Ahyper-parameter refers to a parameter to be set before learning in amachine learning algorithm and includes a learning rate, the number ofiterations, a mini-batch size, and an initialization function.

Learning an artificial neural network may be intended to determine amodel parameter for minimizing a loss function. The loss function may beused as an index for determining an optimal model parameter in a processof learning the artificial neural network.

Machine learning may be classified into supervised learning,unsupervised learning, and reinforcement learning.

Supervised learning refers to a method of training an artificial neuralnetwork with a label given for training data, wherein the label mayindicate a correct answer (or result value) that the artificial neuralnetwork needs to infer when the training data is input to the artificialneural network. Unsupervised learning may refer to a method of trainingan artificial neural network without a label given for training data.Reinforcement learning may refer to a training method for training anagent defined in an environment to choose an action or a sequence ofactions to maximize a cumulative reward in each state.

Machine learning implemented with a deep neural network (DNN) includinga plurality of hidden layers among artificial neural networks isreferred to as deep learning, and deep learning is part of machinelearning. Hereinafter, machine learning is construed as including deeplearning.

The foregoing technical features may be applied to wirelesscommunication of a robot.

Robots may refer to machinery that automatically process or operate agiven task with own ability thereof. In particular, a robot having afunction of recognizing an environment and autonomously making ajudgment to perform an operation may be referred to as an intelligentrobot.

Robots may be classified into industrial, medical, household, militaryrobots and the like according uses or fields. A robot may include anactuator or a driver including a motor to perform various physicaloperations, such as moving a robot joint. In addition, a movable robotmay include a wheel, a brake, a propeller, and the like in a driver torun on the ground or fly in the air through the driver.

The foregoing technical features may be applied to a device supportingextended reality.

Extended reality collectively refers to virtual reality (VR), augmentedreality (AR), and mixed reality (MR). VR technology is a computergraphic technology of providing a real-world object and background onlyin a CG image, AR technology is a computer graphic technology ofproviding a virtual CG image on a real object image, and MR technologyis a computer graphic technology of providing virtual objects mixed andcombined with the real world.

MR technology is similar to AR technology in that a real object and avirtual object are displayed together. However, a virtual object is usedas a supplement to a real object in AR technology, whereas a virtualobject and a real object are used as equal statuses in MR technology.

XR technology may be applied to a head-mount display (HMD), a head-updisplay (HUD), a mobile phone, a tablet PC, a laptop computer, a desktopcomputer, a TV, digital signage, and the like. A device to which XRtechnology is applied may be referred to as an XR device.

The claims recited in the present specification may be combined in avariety of ways. For example, the technical features of the methodclaims of the present specification may be combined to be implemented asa device, and the technical features of the device claims of the presentspecification may be combined to be implemented by a method. Inaddition, the technical characteristics of the method claim of thepresent specification and the technical characteristics of the deviceclaim may be combined to be implemented as a device, and the technicalcharacteristics of the method claim of the present specification and thetechnical characteristics of the device claim may be combined to beimplemented by a method.

1. A method in a wireless local area network (WLAN) system, the methodcomprising: Transmitting, by a multi-link device (MLD) connected to aplurality of links including a first link and a second link, a requestframe including an information field for requesting complete elementsincluded in an element set designated for the second link to a firstaccess point (AP) of an AP MLD, through a first station (STA) includedin the MLD, wherein the first STA operates on the first link; andReceiving, by the MLD, a response frame from the first AP through thefirst STA, based on the request frame, wherein the response frameincludes complete elements included in the element set designated forthe second link.
 2. The method of claim 1, wherein the request frameincludes identifier information related to the second link.
 3. Themethod of claim 1, wherein the element set designated for the secondlink includes an element related to a capability of the second link oran element related to a parameter of the second link.
 4. The method ofclaim 1, wherein the second link is differentiated from the plurality oflinks.
 5. The method of claim 4, further comprising: transmitting asecond request frame for requesting switching of a link connected to thefirst STA from the first link to the second link, based on the responseframe; receiving a second response frame, based on the second requestframe; and performing a procedure of switching the link connected to thefirst STA from the first link to the second link, based on the secondresponse frame.
 6. The method of claim 5, wherein the first STA isconnected to a second AP of the AP MLD, based on the procedure ofswitching the link connected to the first STA from the first link to thesecond link, and wherein the second AP operates on the second link. 7.The method of claim 1, wherein the request frame includes 1-bitinformation for indicating that complete elements included in thedesignated element set are being requested, and wherein the 1-bitinformation is configured as a first value.
 8. The method of claim 1,wherein the request frame further includes an information field forrequesting complete elements included in an element set designated for athird link, among the plurality of links.
 9. The method of claim 1,wherein the plurality of links and the second link are included in 2.4GHz, 5 GHz, and 6 GHz bands.
 10. A multi-link device (MLD) operating ona plurality of links including a first link and a second link of awireless local area network (WLAN) system, the MLD comprising: a firststation (STA) operating on the first link; a second STA operating on thesecond link; a transceiver transmitting and/or receiving a wirelesssignal; and a processor being operatively connected to the transceiver,wherein the processor is configured to: transmit a request frameincluding an information field for requesting complete elements includedin an element set designated for a second link to a first access point(AP) of an AP MLD, through the first STA, and receive a response framefrom the first AP through the first STA, based on the request frame,wherein the response frame includes complete elements included in theelement set designated for the second link.
 11. The multi-link device ofclaim 10, wherein the request frame includes identifier informationrelated to the second link.
 12. The multi-link device of claim 10,wherein the element set designated for the second link includes anelement related to a capability of the second link or an element relatedto a parameter of the second link.
 13. The multi-link device of claim10, wherein the second link is differentiated from the plurality oflinks.
 14. The multi-link device of claim 13, wherein the processor isfurther configured to: transmit a second request frame for requestingswitching of a link connected to the first STA from the first link tothe second link, based on the response frame receive a second responseframe, based on the second request frame, and perform a procedure ofswitching the link connected to the first STA from the first link to thesecond link, based on the second response frame.
 15. The multi-linkdevice of claim 14, wherein the first STA is connected to a second AP ofthe AP MLD, based on the procedure of switching the link connected tothe first STA from the first link to the second link, and wherein thesecond AP operates on the second link.
 16. The multi-link device ofclaim 10, wherein the request frame includes 1-bit information forindicating that complete elements included in the designated element setare being requested, and wherein the 1-bit information is configured asa first value.
 17. The multi-link device of claim 10, wherein therequest frame further includes an information field for requestingcomplete elements included in an element set designated for a thirdlink, among the plurality of links.
 18. The multi-link device of claim10, wherein the plurality of links and the second link are included in2.4 GHz, 5 GHz, and 6 GHz bands.
 19. (canceled)
 20. (canceled)